Samurai 8 The Tale of Hachimaru Vol 1

Samurai 8: The Tale of Hachimaru by Masashi Kishimoto. A Shonen manga rated Teen, published in English by Viz Media.

Hachimaru is a boy too sickly to leave his house, who dreams of being a samurai. When a mysterious cat-samurai arrives and offers him a chance, Hachimaru is reborn as a cyborg samurai and sets out on a journey across the galaxy.