Patients disappeared one after another from a mental hospital. Led by Drome, a wizard from Arabia, as president, the Yokai Club is a group of psychopaths, monsters, and ghosts, all of whom have been ostracized by ordinary people.

They take mentally ill patients out of the hospital and induct them as new members. Ken-chan, the nephew of the director of the hospital, Mr. Mustachio, infiltrates the Yokai Club and learns of their goal of turning the world's people completely crazy. Ken-chan escapes from the club and meets Sachiko Sarutobi, the girl they are after, and tells her about the plans of the Yokai Club. Sachiko has an abnormal constitution inherited from her ancestors, which allows her to use ninjutsu.

The Yokai Club creates a series of incidents that drive the people of the world insane. Drome's evil influence extends to Mr. Mustachio, but then Sachiko appears, and a showdown between Sachiko's ninjutsu and Drome's magic begins.

Another early work of Tezuka's that was omitted from all editions of the complete works and only received periodic reprints under Sun Comics, due to issues in which the contents of the manga could be seen as offensive.

The manga can be found in the Gordon W. Prange Collection and is available as a digital resource at the National Diet Library and the International Library of Children's Literature.