A boy named Hat falls into the underworld realm and discovers the evil Lord Jaku, a demon who aspires to become the new king of the underworld, replacing the current king, Aleph. Hat is locked-up and meets with the prince of the underworld, a fellow named Hotdog. With a common enemy in Jaku, the two join forces and escape from their imprisonment. They are quickly re-captured, but are then rescued by an old man named Grandpa Tau.

After escaping, Tau takes them to a magical shrine, where Hat discovers that he is part of a long lineage of heroes known as "Magical Hat", and he is the next in line to don the hero's hat, adopting its powers to fight evil, but is he up to the task, and can he use these powers to put an end to Jaku's sinister plans?