Yahiko is a samurai descendant. Yahiko's father died during the Battle of Ueno during the Boshin War, slain at the Keneiji Temple. His mother died of syphilis in a brothel to put food on their table not long after giving birth to her son. Yahiko was originally forced to live as a thief for the local Yakuza, who tricked him into believing that he still had to pay off the money the gangsters gave to his mother to buy medicine. With the help of Himura Kenshin and Kamiya Kaoru, he becomes an apprentice of the Kamiya Kasshin-Ryuu style.
Yahiko has a friend/rival, Tsukayama Yutarou and a sweetheart, Sanjou Tsubame, who works at Akabeko.