Kabuto Yakushi

Kabuto remembers when he first met Orochimaru when he and the rest of the Leaf Orphanage aided several wounded Hidden Leaf Ninja, the Sannin member seeing potential in the child despite not interested in becoming a ninja. But that night, when Nonou is blackmailed by Danzo into an intelligence gathering mission in the Hidden Stone Village, Kabuto also ends up in Root's services as he spend much of his childhood infiltrating the villages of the Five Great Shinobi Nations. But while on an assassination mission in the Stone Village, Kabuto fatally wounds an attacker he recognized too late as Nonou. Kabuto tries to save Nonou, but runs off in shock when she did not recognize him and is found by Orochimaru. Orochimaru take Kabuto to his secret laboratory, revealing that Root set up Kabuto and Nonou to kill each other to silence them. Though ordered to kill any possible survivors, explaining that one can forge their true identity with the parts of those they meet, Orochimaru instead offers Kabuto a place as his right hand with the promise of his own identity. Following after Orochimaru's defeat by Sasuke, Kabuto took his mentor’s words literally as he injected himself with various blood samples to become his "true self".