Tatsumi Oga

"Oga" redirects here. For other uses, see Oga (disambiguation).

is the main protagonist in the Beelzebub series.

Oga is first introduced as a strong fighter, beating up some fellow class mates and then making them bow down to him because they had attacked him in his sleep. He was picked to become Beelzebub's parent as he possessed the qualities of the ideal parent for the future Demon Lord: strong, arrogant, and thinks-nothing-of-fellow-man. In addition to the aforementioned attributes, Oga also seems to take pleasure in tormenting others. Oga and Beelzebub cannot be separated by more than 15 meters or else it may result in instant death for Oga, according to Hilda (as of chapter 38, the distance has increased with 8 centimeters). He accidently made a contract with Beelzebub after Hilda wounded his cheek with her weapon at the electric fence.

Appearance
Oga is usually seen sporting a grotesque grin and his demonic features are visibly shown when he is either angry or disturbed. He possesses brown hair and dark eyes, he is rather muscular with a widespread build, and his attire usually consists of a worn-out shirt and plain pants (usually jeans). He has been shown on a few occasions to be wearing either sweatpants, and on one occasion, has even been shown wearing his pyjamas (ironically very detailed with pinstripes going down the side). When Oga attempts to smile, he is usually seen with a demonic, evil grin. This speaks to his lack of social skills (due to his inhibition in a juvenile delinquent high school).

When fighting, Oga appears to have a different look. Aside from his rare comedic entrances (usually as a relief from an intense situation), he is usually very calm and actually quite aware. His eyes are alert and he seems in control of his emotions. Beel does not transfer this emotion however, and is usually shown in a maintained an angry look.

Personality
Initially, Oga was nothing more than a crude and uncaring delinquent whose only friend seemed to be Furuichi. While he wouldn't start fights, he would take deliberate pleasure in inflicting the most pain possible when facing his opponents, regularly resulting to cruel and unusual methods of punishment for his defeated enemies, showing a high amount of sadism. It is because of these qualites that he was initially chosen to become Be'el's parent. Alaindelon described the ideal parent of a Demon Lord as being "strong, tough, self-centered, and cares nothing for his fellow man". These traits sum up most of Oga's personality.

As the series continues, it should be noted that the trials Oga has faced and the new friends he has gained has altered his personality somewhat. For example, when the Rokkisei called out Ishiyama to meet them on the rooftop, he initially came alone. But later on when Himekawa, Kunieda, and Natsume soon arrived, Oga smiled knowing that they have his back. Though he retains his love for his cruelty, he is now much more calm and easier to be around then he was at the start of the series. Still, in his own twisted way, he seems to care for the people that are close to him. When Furuichi was gone during the summer vacation and leaving Oga alone, he called Alaindelon to transport Furuichi back home just so he can hang out with him. Or beating up and embarrassing Miki infront of their school back in middle school. Only because it was to protect him from Kiriya Reiji because he knew that both Miki and Kiriya would move to Nara at the same time, and if Miki was involved, then Kiriya would've attacked Miki in Nara where Oga wouldn't be there to protect him.

Oga doesn't seem to have any sense of appeal nor opposition against girls, unlike Furuichi who is easily seduced and will not hesitate to pick up girls. However, he does also has a sense of chivalry, as said by Hilda, as Oga will not fight or harm a woman. This was proven true when he only dodges during his fight with Aoi, and more recently when fighting the female Pillars he held back when he realize he was about to hit a girl. The only times he actually hits a girl was a sparring match with Aoi to determine if they were capable of learning Black Techs and knocking out Yuchelle by destroying her weapon. It is also hinted that he disapproves of underage smoking and drinking.

As much as Oga hates it, he tends to listens to lectures very well. For example, when Oga was telling Teimō about Baby Beel's demon praying dance, Kunieda quickly takes him to the side and lectures him about being careful who to talk to about Demons and only talk about them who are involved. After that, Oga never told anyone besides (excluding Demons) Furuichi, Aoi, Ittōsai, and Saotome. Another example of Oga paying attention is when Saotome was lecturing Oga about using Super Milk Time for 5 minutes max. Later when Oga uses Super Milk Time, he only fought for 5 minutes after using a huge blast that knocked him into unconsciousness.

As the series progresses, he learns how to put his pride aside and knows when to follow orders. (For example, in Chapter 126,when Saotome said that the Ishiyama students were going to need training with him, all of the delinquents didn't want to train with him because they thought he was an old geezer and was weaker than them and it will take their pride away. But Oga stepped up and said let's go train, instead of being arrogant and keeping his pride, he put it to the side and went to get stronger.)

Touhoushinki Arc
Oga is defeating armed mercenaries and local thugs. As they pleaded for mercy Oga fought them alone, and with an off-screen tilt, he was shown to have battled them rigorously. Many were unconscious, and although it seemed the series was unfolding in an event-themed fashion, it was shown that it was really Oga's retelling of what transpired to Furuichi Takayuki. His story continued and he explained how a large man (Arandron) came floating upstream (the local riverside) and he eventually cracked open, revealing a small baby. Furuichi is shocked by Oga's lack of story-telling abilities (although the retelling was revealed to be true), and the two continue in loud voices. Be'el is completely focused on the conversation at hand and he remained quiet for the most part of their conversation. Oga continues his rant on the Be'el situation and reveals that he must take care of the demon baby, because the child is so attached to Oga's raw abilities. Hilda is mentioned and referenced during his conversation and Furuichi is quite taken by her.



The next day, Oga takes Be'el to school with him. Furuichi wonders out loud why he would go to that much trouble for the kid. The story continues with Hajime Kanzaki's mercenary forces coming in contact with Oga. Furuichi is worried about Oga's status among the students at Ishiyama High. The students are convinced Oga is the father of Be'el and are shocked by their self-perscribed qualifications. Oga becomes aware of Hajime Kanzaki's status as among the four Tohoshinki. Being the somewhat sadistic and irresponsible teen that he is, Oga seeks out Kansaki in an attempt to force Be'el on him. His logic was that "strong men" were most appealing to Be'el, and that the most malicious of characters would satisfy his needs. When the two meet, the discussion takes a dangerous turn as Kanzaki sends one of his own men flying with a direct attack (after annoying him). Be'el was touched on the head by kanzaki, Oga realized that he was rejected as Be'el did not react, and in retaliation, sent Kanzaki flying. Leaving Kanzaki's men completely shocked, Oga leaves the area feeling rather disappointed.



The next step for Oga was handling the other menacing forces of Ishiyama. The second step was Tatsuya Himekawa, another thug who uses his money and influences to gain dominance. He was approached by Kanzaki and easily took care of him, and afterwards, Himekawa went to handle Oga directly. He kidnapped Furuichi and Hilda (both were seen with severe burns). Oga was flooded from head to toe in his room, and was immediately disgruntled. He went to the warehouse where Himekawa held the two kidnapped friends. He blasted through his thugs (reinforcement), and made his way to Himekawa. However, Himekawa turned out to be a more competent opponent than Kanzaki. His weapon was a stung rod and with fluid movements he had Oga on the ropes momentarily. However, Oga simply stated that the shock he received from the rod was nothing compared to Be'el's tantrums. With Be'el's power, Oga was able to send Himekawa flying. Himekawa was later shown, feeling somewhat bitter, in the hospital along with Kanzaki.



After defeating two of the Tohoshinki, Oga claimed somewhat of a celebrity status among the students. Although he did not seem any more out of the ordinary, he was commented on by many of the juveniles that pollute the school. Oga takes Be'el to the park as what he calls his park debut. There he meets a young girl (Aoi Kunieda, not known to Oga) wearing glasses and a stroller. Oga attempts to become friendlier as he does not want to be thought of as cruel or uncaring.

He sits near the girl and strikes up a conversation, the girl was later revealed to be one of the four Touhoushinki, the leader of the&nbsp {C feminine group Red Tail, Aoi Kunieda.

Although she wears a disguise at the park, as a means to protect her reputation, Oga is completely oblivious when the two square off. He is unable to identify her although it appears as though Be'el was able to make the distinction less apparent.

Aoi was the one looking for Oga as he was said to be "breaking a difficult and dangerous balance", an allusion to his complete destruction of both Kanzaki and Himekawa. Aoi quickly proves herself to be a competent fighter, with rapid speed and a clear understanding of martial arts. She wields a wooden sword, and although not an actual sword, she yields the same results as though it were metallic, slicing the window barrings and their reinforcements. Many of Aoi's opponents were surprised whenever she fought with a wooden sword and asked if a wooden sword can actually "cut" things.

Oga is quick to the challenge and avoids fighting her. Aoi is shocked to see that Oga is carrying a child, and as such is thrown completely off guard by him asking her to become Be'els mother. The delinquents surrounding them awaiting to watch the two fight was shocked as well.

Although it was merely his means to ditch the demonic child, Aoi took this as more of an invitation to become his partner, and as such, she became infatuated with him even developing a crush along the way.

Oga's troubled road through Ishiyama continued when the last and final Tohoshinki was revealed. Oga left his house after Be'el showed signs of their severed bonds. He was launched out of his window after showing a hurt and emotional Hilda his theory of leaving Be'el. Although he was only referring to the electric shocks, Hilda smashed him through the window and ordered him to leave. While walking through the park, Oga was attacked by Tojo's top fighter in an alley-way. Their fight was only a means of testing Oga's power, and as such, the subbordiante left without any signs of anger or tiredness, a statistic Oga picked up on well. A confused Oga wondered about the relation the two shared. The subordinate answered calmly and then exited the alley-way, missing his next hit on Oga (which was sure to be a devastating blow).

When Oga awoke the next morning, he noticed Berubo was missing and Hilda was also absent. Furuichi pondered this and spoke openly on why Oga was taking the situation to lightly. A jubilant Oga was cut short on his celebrations, and was forced to go search for the two by his estranged sister. Oga went to look by the river-bed as that was where he first found Be'el. Tojo and his subbordinate were there, and Be'el was also present, this time riding on the back of Tojo. A fight ensued, and with that Oga began to notice issues with Be'el. His glazed eyes were unfocused and the attachment to Tojo was almost abnormal. Oga concluded that the power he had was enough to draw Be'el towards him. Oga demanded to know how he found Be'el in the first place. Tojo answered honestly that he found Be'el roaming the streets. He then took a few jabs at Oga's terrible parenting skills. Be'el was set to be the prize of the fight, and Oga was quickly beat to the point where he succumed to serious injuries. Oga took the upper hand, catching him of guard until he noticed the zebub spell's contract on Tojo's arm. Tojo sent Oga flying and afterwards took Be'el and left the scene. Oga returned home, bitter and angry, to find Hilda and a ghost like creature in his stairway.

The ghost-like creature turned out to be the demon doctor, a physician that is in Muumuu form who Hilda called to assist with the examination of Oga and Be'el. Oga immediately struck a nerve with the two commenting on both their looks assuming they were low-class demons. He wondered why the demon doctor was so animated. The doctor continued his examination of Oga (with a few minor interruption in the form of Lamia his assistant). The doctor determined that the severing of the bond was because Oga was not powerful enough to keep up with Be'el. A bruised Oga relinquished his role as surrogate father momentarily, in an attempt to regain his strength. Oga wondered aloud whether Be'el was better off with Tojo. He was snapped back into reality by Hilda and his fighting spirit eventually returned.

While taking a shower, he was interrupted by Kanzaki's subordinate. He is told to follow him to the scene of a brutal battle between Kanzaki, Hajime, and Tojo. Tojo utterly defeated Kanzaki and Hajime with help from his own subordinate, a bespeckled man with apparent power. Kanzaki and Hajime are forced to work with Oga in an attempt to defeat the mighty Tojo. Oga does not take to this smoothly however, and with blatant disregard, he tries to turn down the offer. However, he sees reason and the three make their way to the school.

Unfortunately the trio is ambushed by local gangs, a tactic used cleverly by Tojo. Kanzaki and Hajime fend off two opponents each and were dumbfounded to notice Oga handling the rest on his own. Unfortunately, the thugs continue to emerge, and the trio find themselves growing tired. Aoi jumps in and fends them off one by one protecting the three from further harm. Her group, Red Tail, is also present and Aoi tells Oga to continue on ahead and find Tojo.



Oga runs into the school looking for Tojo. On his way, he notices fireworks being set off, and he continues on his way towards the location of the fireworks. When the two meet, Tojo reveals that he figured out Oga's the father of Be'el. He inquires to return it, stating that perhaps a fight over him would be more suitable. Oga states his relation to Be'el being more caring and out of friendship, then going to say that it is up to Be'el to decide. The once warped Be'el regains his composure and glazed look, and he creates a demon circle with estranged markings. A force-field is created and the electric prevents anyone from entering. Oga penetrates the shield, doing more damage to himself, and with a cocky smile gives Be'el the same smile he gave him during their training sessions. The two bonded once more and a "Revival" of their core was created.

Oga now deals with Toujo. The fight between the two was full of complacent blows and rigorious hits. Oga had Tojo on the ropes momentarily and intended to land a strong hit to his midsection. However Tojo repelled the attack and made a blitz behind Oga with a killing blow in mind. Oga dodges and sidesteps him and returns to Be'el and Furuichi's location (Furuichi being there on his own accord). Be'el feeds Oga some power, and the contracting Zebub spell is generated. Oga tells Be'el to stay away from the fight, this includes his help with any zebub spell or magic of any kind. Be'el realizes this, and he sinks his power back to himself. Oga continues his fight and takes a blow from Tojo on purpose, as a means to get bind him and engage a suplex-type move, crushing Tojo.

An exhausted Oga limbers back to Be'el stating his win and the two lock eyes. Oga then notices that his arm deformed during the fight. The magic built up and released explicitly through his arm. The blast destroyed the school and the trials at Ishiyama High concluded with Oga reigning victory over the Touhoushinki.

Saint Ishiyama High Arc
Because Oga destroyed Ishiyama, a vast majority of the deliquents from Ishiyama relocated to different schools but a vast majority of them relocated to Ishiyama High's sister school, St. Ishiyama High. The people relocated included Oga, Furuichi, the Touhoushinki, their subordinates, some members of the Red Tail and the notorious MK5. The group was relocated for the time-being when the school is reconstructed as there were no other alternatives, but the students of Saint Ishiyama were displeased by the presence of the delinquents. Oga and the others were immediately targeted and subsequently harassed for the most of their time at Saint Ishiyama. Their presence was monitored through rotations, and the other students avoided the Ishiyama High refugees. However, there was one St. Ishiyama student, Kazuya Yamamura, who admired the delinquents, especially Oga and Furuichi as he thought that they both defeated the Touhoushinki when in fact it was only Tatsumi Oga that defeated the Touhoushinki. Kazuya even went so far as to meet Oga early in the morning at his house, much to Oga’s dismay. Hilda was impressed to see Oga's "underling", quoting that he was "moving up in the world".

Later after a fight with a rival school, Oga and Aoi, who were involved in the fight, were called to the principal's office. To keep up appearances, the two weren't expelled but instead, chosen to keep the other Ishiyama students in line. Despite being told not to go near the St. Ishiyama students, they went to visit Kazuya and were surrounded by two of the Rokkisei, Ichiro Shinjou and Mitsuteru Sakaki. Knowing they would get expelled for fighting, Aoi and Oga both outclassed them without resorting to violence. Aoi sliced off the end of Sakaki's bokuto with a ruler. Oga dodged all of Ichiro's punches, while asking him questions. After realizing their defeat, Shinjou and Sakaki decided to leave. Heading back to their classroom, they then heard that Hajime had gone to avenge Shiroyama for being unfairly beat up by some Saint Ishiyama students. Aoi and Oga arrived just in time to see Hajime badly beaten by Hisaya Miki. When Nene tried to pick up Hajime, she was taunted by Miki and was held back by Oga when she tried to attack him. Before the group left, Miki asked Oga and his friends to come to the school rooftop to fight. After showing up, the Ishiyama delinquents found four of the Six Knights: Miki, Sakaki, Ichiro and Hiromichi. At first, Oga stated that he would fight all of them. He was joined by Tatsuya, Aoi and Shinataro. Each began their own fight while Oga defeated Ichiro with one punch. Afterwards he began to fight Miki, but he was seemingly immobilized after being hit with Miki’s special move. Hajime jumped in to fight Miki, and was sent flying by Oga. (Miki said that if Kanzaki had continued to fight, he would have been severely hurt due to his old wounds. Oga claimed that he did not know anything about this. His only reason for knocking him out was apparently to move him out of the way.) The fight between Oga and Miki resumed. Miki prepared to show Oga his special move but was stopped by Shizuka Nanami and Kaname Izuma.Toujou arrives to fight and withstands Miki's attack to fight Izuma but is dissuated when Izuma releases dark energy. The next day, Oga's name along with everyone who was present for the fight are put on the suspension list, except the Rokkisei, but are given a chance if they defeat them at a volleyball game during the festival. After being tricked into playing, initially not caring for Hilda's edited flim, Oga skips a day to fight Miki but is defeated by the Izuma style finisher (the Black Owl Killer), although this attack is strong enough to take down Oga in one hit, it must be stressed that Oga actually intended to take the blow to measure Mikki's strength, and made no effort to dodge it. After his pride is hurt, he spars with Toujou in order to make a new move. The day of the festival arrives as Oga finishes his new move, and the volleyball match begins. After having a rough time, they use Be'el to feint and won the game, but after their victory, the school is attacked by one of Oga's old enemies. Miki moves to fight the opponents and is at first overwhelmed, Oga, realizing that Miki can't take them all on by himself, joins in the fight, The others go after the enemies holding people hostage. Oga almost blew his secret but is covered by Izuma, who knows about demon's power. At the end of the festival, Ishiyama is accepted as part of the school.

Prince En Arc
After the invasion by Kariya is over, Oga is seen talking to Hilda about Izuma knowing about demon energy and the next day heading to school remembering how he never got any info on Izuma while at school he is seen being greeted by St. Ishiyama students, then being asked by Miki to walk home together (but quickly refuses him). He then later goes to the roof to confront Izuma himself while meeting Toujou at the same time, but before they fight all three are attacked by Zenjuro Satome (his new homeroom teacher) and is brought back home. Later as baby Be'el slapped him back to life in class he then goes with Furuichi to get something to drink, feeling Zenjuro's energy as he closes the wormhole Oga made during the festival. Feeling the energy, he travels to the gym as Zenjuro is leaving after restraining Hilda as Zenjuro leaves he tells Oga to come to school tomorrow. He is then confronted by Kuineda about who baby Be'el is; as he tries to explain, he hurts baby Be'el's feeling because he doesn't remember his full name. As baby Be'el runs into a wet nurse who looks like Hilda as she knocks out Furuichi, who was listening in. She tries to kiss Oga but is blocked by the real Hilda.

As two other wet nurses come in, a boy who calls himself En appears as he names himself baby Be'el's brother, but before he says more they move to Furuichi's house. After explaining his purpose to destroy the world with Be'el, En and his wet nurses soon disappear after explaining that some En's men will come for Oga's life.As Oga, Hilda, and Kuineda head home, a moment of silence came. When the time that Kunieda must part ways because her home was the other way, a demon suddenly appeared and caught her. Oga and Hilda came up with a plan to save Kunieda, with Oga acting as a bait so Hilda could save Kunieda. The plan went just as planned, but the demon read their tactics. Hilda got pierced with the spear of the demon, right through her stomach. Falling helplessly on the road, baby Be'el was about to cry until Oga stopped him, saying that Hilda was still watching over him. Oga comments that even though she has a hole on her stomach, her concern was still Baby Be'el. Enranged because of what happened, Oga fought the demon even though it was no use fighting. Zenjuro suddenly appeared and stopped the demon before it was too late for them. Hilda was soon taken care of by Lamia and Dr. Folcus. Later that night, Hilda apologized to Oga saying that what happened earlier was a pathetic story. She was planning to say more, but inadvertently fell asleep. After being defeated easily, Oga takes up Kuineda's grandfather's offer for training. After compelting the training, he then started training with Zenjuro; fighting a copy of baby Be'el to be able to use his demon powers.

Once Oga finished his training he went to where Hilda and the others were to fight the demons, hold ing Alaindelon like a sword and when the fight begins Oga shows all his power defeating the demon, who had previously defeated him and Hilda, with one shot. He then turns to the two remaining demons and claims to show them a new skill to beat them at the same time. He then takes a long time preparing a milk bottle, bringing its temperature down, and to everyone's surprise, drinks it himself. He calls the skill "Super Milk Time", which was invented accidentally during his training with Zenjuro. Hilda realizes that he had "forced a synchro", or synchronised himself and Baby Be'el.

After a while, he drinks a bit more milk, causing a complete synchronization, uniting himself and Baby Be'el into one body. However, with Beel, not Oga in control, the demons are defeated, but Himekawa's apartment building is completely destroyed. Prince En leaves with his nurses and Behemoth's demons after making a fit over his interrupted game and Furuichi's misunderstood act of guarding Lamia from the falling ceiling, declaring that he would be back one day with a whole army to crush them.

Akumano Academy Arc
The day after the fight, Oga is seen unconscious with Beel at his side.After the fight with Behemoth's fellow, Oga and Be'el faint. When they woke up they exchange their bodies, so Oga is stucked in Be'el's and Be'el is stuck in Oga's. Together with Hilda, Oga goes to Saotome's place so that he can help him and Beel returning to their respective bodies. Anyway, Beel in Oga's body flees and meets Aoi. He hugs and stays close to her, and because of this, Hilda gets jealous. The two Women fight on the roof, but this Time, Aoi is stronger after her training, and beating her is not a simple task for Hilda. Suddenly, Beel-Oga hugs Aoi and she blushes; Hilda gets even more pissed, and Oga-Beel also wants to stop Beel-Oga. The 3 attack Beel-Oga at the same time, but in that instant, Oga returns to his own body, resulting in Him being hit. Later Oga meets an old man, who was searching for him until that moment. Oga doesn't mind the old one and says he's not Oga at all. The old man then is revealed to be Behemoth and after fighting with Saotome, The School Principal Genma Isurugi and Aoi's Grandpa Ittousai Kunieda, he reveals to have rebuilt the Ishiyama High and renames it as Akumano Academy, a school of demons. After that Behemoth claims to not be the Army Leader because of his advanced age. The actual leader is the likely son of Behemoth (he calls him "Pops"), Jabberwock. He kidnaps Hilda with his dragon Sodom, and flies away with his father on the "pet's" back, while Oga is unable to follow him because of Ittousai blocking him on Saotome's order. But Oga manages to free himself and goes after Jabberwock and Behemoth on the dragon's back. He goes in Super Milk Time again, first drinking 30cc and attacking Jabberwock. Anyway the army general is too strong and easily takes on a triple 3-Hit Zebul Emblem Combo from 30cc Oga and even drinking 50cc of the milk, Oga can't keep up with him. So He decides to hit the dragon and free Hilda; The Wet Nurse orders the BoB Brawler to go away by himself but Oga's resolute, and hits Sodom with a 6-Hit Zebul Emblem Combo. The dragon actually releases Hilda from his mouth, and she uses her demon aura to catch Oga. After she tells him he's a damn fool, she says that he must take care of Baby Be'el, being the only parent he has in this world. Then she gets swallowd by Sodom, letting Oga fall down and the two Demon escape.

Later Oga wakes up and realize that he's in the school nurse office realizing that he was still too weak to face them resolves to train harder to face them again. After training and falling unconscious he has a dream where everyone is in the court room again saying how weak he is at the moment. When he wakes up, he realizes that he's on a ship with Aoi and Lamia. They sail to an island called Decapitation Island where he and Aoi will train to learn how to use demonic energy with Lamia. They were going to the island to learn Black Techs from Suiten Ikaruga.

After copleting his training, he invades Akumano Academy on his own to confront Jabberwock once again and save Hilda, taking down all the Pillars and Pillar Heads who stand in his way, and after Tojou, who appearantly re-built the school, joined him, he reaches the rooftop and rescue Hilda before she is killed by Jabberwock.



Oga and Tojo finally confront the army's leader, as the fight starts, Oga and Tojo cooperate to defeat the powerful enemy, dealing powerful blows such as a full power Zebul Blast and a German Suplex, to which Jabberwock easily resists. After having knocked out Tojo, the fight becomes a One-on-One between The Demon Lord's Father and the Army's General. Oga unleashes Beel's Demon Power drinking all of his milk, but Jabberwock is still stronger than the BoB Brawler, and appereantly defeats him. Just before fainting, Oga stands up, and says he's not done yet, and incredibly deals a powerful kick enough to make his foe fly for a good 10 meters. Jabberwock claims that Oga's power has been finally "awakened", but Oga denies, saying that his newly found strength is not due to such an easy power-up; He says that he's just trying harder to protect Beel, but Lamia says that Oga's strength is due to the fact of him becoming stronger together with Beel, since Black Techs accelerated the Baby's maturation process. Jabberwock can do nothing against the contractor, and collapses after a destructive punch of Oga, which destroys the newly built school.

Memory Loss Arc
In the morning after the fight with Jabberwock, Hilda wakes up and it's shown that she has lost her memory, so Oga and the rest of the family have to explain to her who she is, by their point of view, making Hilda believe that she is Tatsumi's wife and Baby Beel's biological mother. Hilda even makes Oga a bento when they go to school and forces Beel into clothes.

As they try to regain Hilda's memory, one of the pillar squad communicate with them (Oga, Furuichi and Yolda) by using a computer. He said that the only way to recover her was to kiss her. At first, they thought it was a lie. But then, he said that "Every woman needs a kiss from his prince charming". With an answer like that, Oga thought that it was him to be kissing her. So, he smashed the computer (computer from the computer's room) by using the keyboard. Oga asked Furuichi and Yolda whether they heard or saw anything from that event because he can't accept the truth if he was the one to be kissing her. Then, Yolda tells Kunieda, the Red Tail, Himekawa, Kanzaki, Natsume and Good Night Himokawa about the kiss. They chased Oga and told him to kiss Hilda.

While he was hiding behind the bushes, he met Lamia who has brought the antidote for Hilda. But, Hilda was missing. Oga used Baby Beel to locate her and found her by the river. Then, a few pillars who were fishing crayfish met Hilda and wanted to take on a revenge after all she had done to them. She didn't understand anything at all; being a wet nurse and serving a son to a Demon Lord. Furuichi and Yolda were shocked. Oga stopped them when they tried to go to Hilda. He went to her by himself and kicked those pillars into the river. He talked to Hilda about the antidote and she said that she will take it. But then, Baby Beel threw the antidote into the river because he didn't want Hilda to turn back to normal. Oga didn't mind at all. He said that it's okay if she stays like that forever because the good thing now is that she can cook well than before.

He gave Baby Beel to her and said that she was her mother after all. Baby Beel kissed her. Then, she asked Oga whether her cook was really bad and he said that it was almost attempted murder. He said that it was like a chemical weapon. "Do you think you've actually grown a pair, bitch? Fine. Next time, it won't be attempted murder!", said Hilda to him after he insulted her cook as a chemical weapon. Oga freezed when he knew that the 'prince charming' was actually Baby Beel and that she had turned normal. He was attacked by Hilda as soon after that.

Fighting Style
Oga, even before meeting Baby Beel, has only used his fists to fight. He uses street fighting techniques and his already inhuman strength to win fights. He also knows a lot of wrestling moves like the German Suplex and Boston Crab. Now that Beelzebub is with him his strength has been further enhanced with demonic energy. Oga likes to make up crazy names for his attacks even though they're still only regular moves.

As most thugs in the series, he lacks any particular technique in fighting, mostly relying on his natural prowess to diminish the advantage of trained martial artists like Kunieda and Miki. However, he has figured out some classical techniques from wrestling: he defeats Tōjō with a suplex and leads Baby Be'el in a Clothesline, an Elbow drop, and a Boston crab.

He is able to hold his own against a Demon for some time without resort to Demonic power (although he did use the Zebub Blast against this enemy, it had no effect). He can feel Saotome using his demon power, which shows he has notable strength for a human. Later, though, upon having to be rescued from a confrontation with a demon by Saotome, he becomes irritated by the fact he is unable to protect anyone and decides to take formal training from Kunieda's grandfather.

More recently, Oga is training in the Shingetsu style with Kunieda and Kunieda's Grandfather. He has shown to learn at a fast pace, splitting stones and even boulders bigger than himself with the Shingetsu's style basic technique: Nadeshiko. Nadeshiko is a technique were the user focus his or her power completely on a single spot. This technique is also known as the Armorpiercer.

Attacks: (mostly made up by Oga on the spot)
 * Street Fighter Techniques - Psycho Crusher, Shouryuuken, Yoga Chop, Rocket Punch
 * Finishing Moves - Super Rocket Punch (regular punch), Infinity Rocket Punch (regular punch)

Shingetsu style:
 * Nadeshiko - A technique that allows Oga to split a rock in half.

Contractor Techniques

 * : The spell on his right hand expands and grows, moving up his arm and spreading across his face. The more it expands the more Oga's power grows. First, when he lost control against Kiriya the Zebul spell temporarily extended up his arm, over his trunk and across his face. After his training with Saotome, he's able to recreate that state through drinking the Super Milk, but his Professor warns him that if it goes any further that, he might not be able to become human anymore.
 * : Oga punches his opponent and releases a large amount of demonic energy that's strong enough to destroy a building. After his Ankokubutō training Oga can use this attack freely without having to wait for his energy to build up.


 * : Oga uses the Zebul Spell to target his opponent, then punches it until the enemy explodes from the massive power build up. Through Super Milk Time he can stand on the emblem in mid-air and use it's explosion to increase his speed. Oga can also attack with more than one emblem at once when used in conjunction with Super Milk Time. After his training with he developes an even stronger version of Zebul Emblem called Ankokubutō: Zebul Emblem which took out Basilisk in one blow.


 * , also known as : when Oga drinks the Super Milk to remove the limiter between Beel and himself, causing them to become synchronized. The Zebul spell spreads all over Oga's body and he becomes faster, stronger, and takes on Beel's personality. He can also use the Zebul Emblem to a much larger extent. Saotome says Oga can only use it for 5 minutes or else he'll become a demon permanently. If Oga drinks the whole bottle of super milk and becomes completely synchronized with Beel. Oga gains wings, darkened skin (in the anime his skin colour doesn't change but his hair colour turns from brown to green, much like Beel's) and a binky like Beel's in this state. While synchronized with Beel, Oga gains enough power to easily overpower two demons and injure Saotome's arms when he attempted to guard it. In this state, he looks to be capable of using an appereantly infinite number of Zebul Emblems, which he can use to create a huge explosion that can destroy a skyscreaper. After his Ankokubutō training Oga seems to have mastered this state. Due to his training, Super Milk Time can now be controlled up to 400cc, shown when he went up from to 30cc to 80 cc with no apparent side effects. With 30cc he was able to defeat 6 Pillars, and with 80cc he was able to beat the Pillar Baron Basilisk without any injuries.

Abilities

 * Enhanced Strength: Even without his demon powers, Oga has shown a high level of strength in combat. At several points throughout the story, he is shown to be able to send people flying with his punches and even crush solid stone using his enemies. He's also able to lift a boulder and Alaindeon with ease, which are both larger than he is. After his Black Tech training his strength increased even more, to the point where he can easily over power demons who are not Pillars or higher.


 * Enhanced SpeedL Oga is shown to be extremely fast, most notably when he was almost able to keep up with a motorcycle going 50 kilometers per hour, and later when he was able to dodge Aoi Kunieda's attacks at close range. After his Black Tech training his speed has increased greatly. Oga is quickly able to take out a group of non-pillar demons, even quickly taking out one who was sniping him in seconds by jumping up the side of a building behind him.


 * High Electricity Tolerance: Due to being shocked by Be'el numerous times, he has grown a sort of immunity towards electricity, as shown when he was able to block Himekawa's stun baton (which was 12000 volts) with no negative effect. He states further that Be'el's electricity is a lot more effective.

Beelzebub IV
{C Oga and Be'el share a unique relationship as Oga's personality would seem to contrast with his role as a parent. Oga spends much of the first arc trying to pass Be'el on to someone stronger and more evil than him, resenting his current role as a parent to the future demon lord. After Be'el is taken by Toujou, Oga admits that he still doesn't want to look after him, but accepts that Be'el wants him to be his parent. After all the time they spent together, they've formed a close bond, and Oga seems to act more friendly towards Be'el. They've gotten close enough that Oga can understand Be'el's way of speaking. Oga, even if he is not interested in the fate of humanity, states that he won't let Beel destroy it because all this is stupid and since he is his parent, Beel will not do something so useless, indicating that Oga truly accepts being the father of Beel.

Takayuki Furuichi
Furuichi is Oga's best and, at the beginning of the series, only friend. (Quite possibly because he was the only one willing to put up with Oga and his antics.) Because of the differences in their personalities, the two spend a considerable amount of their free time arguing. However, in a dangerous situation, they band together and work well together. Oga is frequently willing to do things at Furuichi's expense, often thinking that Furuichi himself won't mind. It is a reacurring theme, mostly used for comic effect, that they are able to communicate without saying anything aloud, showing their close bond and great understanding of each other.

Hildegarde
One of the most complex relationships of the series. Hilda often looks down on him and never hesitates to mock him. In turn, he finds her cold and manipulative personality annoying. However, it is shown on rare occasions that they do care about each other, such as when Hilda thanks him for helping her get Beel back from Toujou and when Oga became enraged at Hecatos for harming her. It should be noted that the two work extremely well together in a fight. They are also known as 'The Most Evil Couple' and 'The Strongest Husband and Wife'. Hilda is already considered as Oga's apparent bride/wife by the whole Ishiyama school and his family, thus gaining her nickname, "Oga'sbride/Wife/Wifey". Both of them (Hilda and Oga) don't really bother to correct other people's opinions, considering it's a waste of effort to explain. As the chapters pass by, Hilda's and Oga's relationship has grown in leaps and bounds naturally, even Oga's family has accepted her presence as a family member, especially his sister Misaki. Although their constant bickering is still present, Hilda gained Oga's utmost respect and also vice-versa.

A pinacle point in their relationship occurs when Oga saves her from being kidnapped by Jabberwock. Realizing that Oga's tactics wouldn't stop Jabberwock, she pulls Oga close and tells him that she is leaving Beel in his care alone, giving him a rare sincere smile. She then allowes herself to be taken by Jabberwocks dragon in order to save Oga and Beel, her parting words being "You're...the only father he has in this world" implying she has finally accepted Oga as Beel's parent. Oga, on the other hand goes as far as to breaking into Demon high school alone in order to rescue Hilda.

When Oga arrived at Akumano Academy, he received a very loud scolding from Hilda. She said that he was endangering her master, Be'el, again and that he was being very reckless and stupid. But Oga shouted back, with the same intensity as her voice level, that he came all that way just to save her and she should shut her mouth and wait for him. Surprised, Hilda's eyes widened and she stayed silent. As the battle between Jabberwock and Oga unfolds, Oga made the rescue of Hilda as his top priority. Being impatient, Jabberwock surprises them with a beam of demon power aiming towards the crucified and almost unconscious Hilda. Oga moves quickly to get Hilda before getting hit by the blast. The barely awake Hilda caressed Be'el's cheeks and told him how glad she was that Beel was safe before completely falling out of consciousness. Jabberwock laughed and commented on how stupid she was. Oga became filled with anger and told him to not laugh at her. He attacked him due to him mocking her loyalty towards Baby Beel.

By the time the Akumano Academy arc ends, his care for her has grown even more, admitting that he cant bring himself to tell Hilda, who was experiencing total memory loss, the truth about their situation simply because he saw how happy she was. But he seems to be shy when people said Hilda is his wife. As time passes, he gradually becomes more fond of Hilda, while trying to help her regain her memories. In the end Oga accepts 'New' Hilda saying that regardless of which personality she has it doesn't changes te fact that she is Beel's mother. And that now he actually enjoyed her food. She is one of few people, including his own family, that he allows to call him "Tatsumi".

Aoi Kunieda
Out of all the characters in the series, Oga treats Kunieda the nicest the most. Oga first meets Kunieda in the park for his park debut. (She was in disguise). After failing to make any progress for his park debut he sees Aoi laughing when Oga is called a murderer so he approaches her and puts his hands on her shoulders and asks Kunieda to go out with him. At first, she is shocked and thinks that he is to asking her to go out on a date. Only to realize a while later that he actually meant to help him out with his park debut. When she arrives at school alongside Nene and Chiaki she searches for him assuming that he is a bad guy that had caused so much violence and so many people to be hospitalized.So to prevent Ishiyama from being destroyed by him she picks a fight with him. Kunieda catches his attention due to her display of her strength.He hands over Beel to her after their second confrontation, but Kunieda declines and believes that Oga is the father of Beel. Oga explains to her that he is not his father but he is forced to raise him.

He is nicer to her when she is in disguise (Aoi Kunie) such as buying her ice cream when they meet again in the mountains. Due to his dense personality, Oga fails to realize that Aoi Kunieda and Aoi Kunie are the same person. As the series progresses, Kunieda starts to show more interest in Oga,such as asking his number so she has a way to have contact him.Due to training together and having spent so much time together they start develop a relationship based on friendship and trust.

Hidetora Tōjō
Oga and Tōjō has a 'frenemy' relationship. They don't mind competitively fighting against each other just to know who's stronger, but they're still able to communicate and joke with each other like friends. In a twisted way, they enjoy fighting each other, a good example is when after Oga was beaten down by Miki, he went to Tōjō and asked him to a fight. As they were pounding each other, they were laughing and enjoying it. Since the Tōhōshinki arc, the two have apparently developed a decent friendship with one another.

Hisaya Miki
Oga, Furuichi, and Miki were friends during middle school. Oga met Miki when Miki was getting beaten up by thugs until Oga came by and rescued him. During Miki's last day at middle school with Oga, Oga pretended not to know Miki beaten him in front of everybody and Miki resented Oga ever since. However, after learning the truth, Miki then realized that Oga never had forgotten about him. After the incident with Teimō, he and Miki tried to tighten up their friendship again.

Kazuya Yamamura
Yamamura admires Oga greatly and wants to be his disciple. Yamamura praises him deeply and calling him "bro" which Oga finds to be flattering, despite not having wanted Yamamura as his disciple initially.

Jabberwock
Jabberwock immediately dismisses Oga as an unworthy opponent on first meeting him, but he develops a little amount of respect for Oga on fighting him for the first time. When he faces Oga a second time he sees Oga as a worthy opponent and happily battles him and Tōjō. During the battle he was happy of Oga's strength and wore a smile through the battle. And said it was fun.

Quotes

 * "Bow to me!! (his catchphrase)'''
 * "Men are fighting spirit." (to Furuichi)
 * "Men... don't freak out crying. You'll be made fun of." (to Beel)
 * "...I don't want it either." (referring to Beel)
 * "What the hell do you think you're doing? You cut our link to protect me?! Who the hell do you think you are? Your electric attacks... are nothing more than a little static electricity to me!" (to Beel)
 * "Neither. I fight just for me. First off... that brat's not even mine. It's the exact same thing as you; I picked him up and took care of him that's all. Whether he comes back to my place or stays stuck to you, thats... up to him." (to Toujo referring to Beel) 
 * "It's time to eat!!" (to Beel)
 * "Let me tell you something good... Beel won't destroy the human world, Do you know why? It's because I'm his parent, I won't ever let him do something this stupid." (Oga to Naga)
 * "Idiots are not good!"
 * "I've always wanted to do it with you.."(to Kunieda)
 * 'I'm here to rescue you, Dumbass! So shut up and wait for Me!!" (to Hilda)
 * "This doesn't even hurt compared to when baby Be'el cries at night." (to Himekawa)
 * "Bring it!" (to Jabberwock)
 * "Don't you dare laugh at her!" (to Jabberwock referring to Hilda)
 * "Regardless of what personality you have, it doesn't change the fact that you're his mother." (To Hilda) 
 * "She's in a bitchy mood" (To Beel, referring to Hilda)
 * "And this is why you're known as 'Creepichi'" (To Furuichi)
 * "You can't catch crayfish in the winter. They go into hibernation" (Referring to the Pillars)
 * "Damn that Furuichi. He let the cat out of the bag! When I find him, he'll experience a fate worse than death!" (Referring to Furuichi while hiding in the bushes)
 * "Huh? It went beyond the point of bad. It was attempted murder! It was like a new chemical weapon." (To Hilda, referring to her cooking)

Trivia

 * The first part of his first name, Tatsu, means Dragon. This is a play off the eastern mythology of the Tiger and the Dragon, in which Oga is the Dragon and Tojou Hidetora (Tora) is the Tiger.
 * When Oga switched bodies with Beel, he stated that he wanted to play the piano.
 * Oga is famous for his demonic smile, along with Beel.
 * While Oga's hair is portrayed as dark brown in the anime and manga, some chapters depict it as being a lighter brown.