Attack of the Twin Demons

is a technique that allows Sakon and Ukon to merge their bodies using their kekkei genkai. Typically, Ukon is dormant within Sakon's body, with only his head protruding from the back of Sakon's neck, although he can move freely inside of and protrude any part of his body parts from anywhere on his brother's body.

Trivia

 * When Kabuto Yakushi used this technique in chapter 585, he called it "''. Kabuto's usage is also merely a copy of Sakon that has the ability to access the DNA of and change into the other Sound Five members (Kimimaro, Kidōmaru, Tayuya and Jirōbō) and Orochimaru through the integration of their DNA into Kabuto's main body.