Samurai 8: Hachimaruden

Samurai 8: Hachimaruden (サムライ8 八丸伝, Samurai 8 Hachimaruden) is a Japanese manga series written by Masashi Kishimoto and illustrated by Akira Okubo.

Plot
The galaxy is headed towards the end of its existence: It can’t withstand any longer than for another century. A samurai was given the mission to try and save all of the scattered planets and their respective inhabitants by finding "Pandora's Box". The warrior god, Fudo Myo-o, sealed a secret that will save the entire world inside of Pandora's Box. In order to open it, someone will need to find the seven keys first. Hachimaru, a feeble boy who’s required medical assistance since birth, might just be one of them!

He can't run! He can't eat hard food. You can't get any weaker than the boy named Hachimaru. But his dream is to become a samurai. For a boy who can't even survive without the help of his father, that dream seemed impossible. But when a samurai cat appears before him, his whole life will change!