A young monster boy was born between a human and a monster king who rules the world of monsters. During his training in the human world, his father was killed by the rebellion of the evil monster army led by the demon king, and his mother was imprisoned in a cane. Ugly monsters stand in his way one after another as he continues his journey in search of clues about the hated Great Demon King... despicable traps... Will the Yokai Boy be able to defeat the Great Demon King and restore peace to the monster world once again?