Two souls travel alone and secluded in their various worlds, living radically different lives. Ren, nine years old, has lost the only person who treated him with respect, and he is shunned by what remains of his family. Ren flees into the perplexing streets and lanes of Shibuya, where he has no parents, no genuine relatives, and no else to go. Ren meets the fearsome Kumatetsu, who guides him to the beast kingdom of Shibuten, through the twists and turns of the alleys. The boy symbolizes a chance for Kumatetsu to become a contender to succeed the Lord of the Realm when he retires. Despite being practically unequaled in battle, Kumatetsu's icy demeanor has left him with no disciples to train.