The boy who would become Sanosuke Sagara began life living in the Shinano Province where he lived with his family, but at the age of nine he left home to join the Sekiho Troop. However when the Meji goverment deemed the troop to be useless, the entire troop besides Sanosuke, leaving Sanosuke with a deep hatred for the government. As Sanosuke grew he became exceptionally strong, being perhaps the only person to be strong enough to use the sword zanbato, leading to his nick name of Zanza.
Sanosuke begins the manga being hired by a former enemy of Kenshin to assassinate the wanderer, but following being defeated becomes a close ally, over several battles where he fought alongside Kenshin. Eventually a former enemy of Kenshin’s,Saito returns to the dojo, during which he attacks Sanosuke wounding him badly, in an effort to judge Kenshin’s skill without his vow to never kill to interfere. Kenshin eventually leaves in order to slay Shishio without telling anyone farewell, this along with the teasing of Saito spurs Sanosuke to follow and train along the way.
During Sanosuke’s journey he becomes lost in the woods, where he comes along fallen monk Anji,who becomes his teacher at the technique Futae no Kiwami, which makes Sanosuke vastly stronger. Eventually he arrives where he goes to battle Shisho and the Juppongatana.During the entrance into Shisho’s stronghold, Sanosuke is the first to battle where he quickly is forced to fight his teacher Anji. Sanosuke eventually manages to reach Anji, who gives up on his violent path allowing Kenshin and Saito to continue on.