Samurai Eight: Hachimaruden Wiki

The galaxy is headed towards the end of its existence: it won't make it another century. A samurai was given the mission to try and save all of the planets and their respective inhabitants by finding Pandora’s Box, inside of which the Warrior God Fudo Myo-o sealed a secret that will save the entire universe. In order to open it, the Seven Keys must be found 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!