The Boy And The Beast, Vol. 2 (Manga)

A lost boy in Tokyo, Kyuta, slips into an alternate universe, where he is raised by a bear-man, Kumatetsu, who fights for a living.

Having wandered into the beast world of Jutengai, Kyuta's gotten himself a master--Kumatetsu. But it turns out Kumatetsu's not quite as good at teaching as he is at brawling. The grandmaster sends teacher and student alike on a pilgrimage, asking all the wisest beasts in the world a simple question: "What is true strength?" But are the boy and the beast ready for the answers?