"Kabuto Yakushi" (薬師カブト, Yakushi Kabuto) is episode 336 of the Naruto: Shippūden anime.
Kabuto has a flashback of when the Konoha Orphanage aided several wounded shinobi — through which Kabuto was tasked with healingOrochimaru. Seeing talent in the young man, Orochimaru asked whether or not he wants to become a shinobi, to which Kabuto declined, saying he is not interested in the job. During nighttime at the orphanage, Nonō is approached by Danzō along with Orochimaru and Tatsuma Aburame. Danzō and his men seemingly blackmailed her into going on an intelligence gathering mission in Iwagakure, much to the other orphanage caretakers' dismay. Also recruiting Kabuto in the process, he is tasked with infiltrating the villages of the Five Great Shinobi Countries. While on a mission in Iwagakure, Kabuto encounters Nonō — whom he had critically wounded. Attempting to heal her, Kabuto is shocked upon hearing her stating that she didn't remember him. As he wonders why Nonō forgot about him, he is once again approached by Orochimaru. Following Orochimaru to his secret lab, Kabuto learned the truth about Root's plan to dispose of both him and Nonō. Kabuto then makes his decision to join Orochimaru and serve as his personal spy. After Orochimaru's death, Kabuto injected himself with blood from the latter's remains — as part of his quest to find his "true self".