The Boy and the Beast, Vol. 2 (manga) — Mamoru Hosoda

Having accidentally wandered into the beast world of Jutengai, Kyuta has 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 answer?