Kabuto Yakushi

Kabuto Yakushi is a major antagonist in the Naruto series. He is rogue ninja who originally worked with Orochimaru before striking out on his own and becoming a more dangerous threat to the protagonists in his own right.

Past
When Kabuto was a child, he was found outside a destroyed village with a head injury and no memories. He was brought to an orphanage where a nun named Nonō Yakushi treated him and due to his shyness, said nothing to anyone, not even thanking Nonō for her kindness. Thus one of the other orphans, Urushi, asked if Kabuto had any manners, before putting a helmet on his head to protect his head wound. Urushi said his lack of a name was annoying and Nonō, taking inspiration from the helmet, decided to call him “Kabuto.” That night, Kabuto, feeling guilty because he didn’t thank Nonō, got out of bed to look for her. However the other wards caught him and he got in trouble for being up past curfew. They brought Kabuto to a clock to teach him the time of curfew and at first, it seemed like he was too young to know how to tell time. However Nonō saw he was squinting and gave the boy her glasses, letting him figure out the curfew time. Since the orphanage couldn’t afford to get glasses for Kabuto, Nonō allowed him to keep hers. The boy started crying in gratitude, thanking her over and over as she consoled him.

As he grew up, Kabuto learned medical skills from Nonō, helping her heal shinobi and raise money for the orphanage. This led to his first meeting with Orochimaru, who suggested that he become a shinobi, but Kabuto wasn’t interested. But later, the boy overheard Nonō talking with Danzo Shimura, who wanted an orphan in exchange for his funding the orphanage. Kabuto took him up on the offer and would be assigned to missions, infiltrating hidden villages. On one of these missions in Iwagakure, Kabuto’s cover was blown and he had to retreat, accidentally attacking Nonō as he did so. She was unable to recognize him, even as he was healing her injuries, and Kabuto started to reflect on and question his purpose in life. Kabuto was again approached by Orochimaru, who told him that his fight with Nonō had been orchestrated by Danzo as Kabuto has become to mush of a liability due to his skills. Furthermore, having been show photos of what she was made to think was Kabuto, Nonō was tricked into killing him on the promise that Root would release him from his position. Orochimaru went on reveal his position to kill the survivor and enraged Kabuto by pointing out that Root's missions have made him devoid of an identity to truly called his own.

However, admitting he sees a bit of himself in the the youth, Orochimaru offered him a new identity and a position as his right-hand man in the Hidden Sound village. Orochimaru did indeed give Kabuto his new identity, that he’d been found at the Battle of Kikyo Pass and he’d been raised by a captain in the Konoha Medic Corps. Kabuto was later sent to spy on Sasori for Orochimaru, however the Akatsuki member used a technique to make him his own sleeper agent. But Orochimaru was able to break Sasori’s control over Kabuto, who would continue to pretend to be the Akatsuki member’s servant so as to find out about the Akatsuki’s plans. During Kabuto’s time in Konoha, he attained the rank of genin and took part in the Chunin Exams, so as to gain information on the other participants for Orochimaru.