RK: Yahiko

Myojin Yahiko is an orphan from a samurai family and was forced to work as a thief to repay the debt that he had supposedly owed due to his parents death before they could pay it back. When he meets Kenshin, he is saved by Kenshin and decides that he would grow up to be just like his savior. But due to Kenshin's strong beliefs in not teaching anyone else the sword style he had obtained, he enlisted Yahiko to be trained by Kaoru at the Kamiya Kasshin-Ryū.

(taken from wikipedia)
Ruroni Kenshin was written and illustrated by Nobuhiro Watsuki.