The Boy and the Beast follows Kyuta, a lonely runaway boy in Tokyo who stumbles into the fantastical realm of beasts and is taken in by Kumatetsu, a gruff, brash bear-like warrior. The story centers on their unlikely father-son bond as they train, clash, and grow together, with Kyuta eventually returning to the human world as a teenager. Readers enjoy it for its heartwarming portrayal of found family, personal growth, and the struggle between two identities, along with its dynamic blend of action, humor, and emotional depth.