Based on the manga Mamonogatari Itoshi no Betty created by Koike Kazuo and Kanou Seisaku.

Betty, a devil-girl with the face of an angel and a heart of gold, falls in love with a human gangster, Danpei Kimogawa, when they meet during a rainstorm. They end up living together in Tokyo - though Danpei has trouble coping with his new in-laws, a witch and a demon, who like dropping by at inappropriate moments.

Betty has actually been sent to the human world on a mission to defeat the demon Lutan. While Betty continues her task, her skeletal grandmother sends nubile nymphs to tempt Danpei and see if he is suitable husband material.