Oga Tatsumi (voiced by Konishi Katsuyuki) is a freshman at Ishiya Demon High School. He is a bad boy with fierce eyes and a violent personality. On this day, Oga, who had just finished a fight by the river, found that a very suspicious-looking uncle was floating on the river. What shocked Oga was that a small baby was born in the uncle's body! The uncle told Oga that his name was Alandron (voiced by Takagi Wataru) and the baby was called Little Beru (voiced by Sawashiro Miyuki). They came from the demon world, and the purpose of this trip was to destroy all mankind! Inexplicably, Oga signed a contract with Little Beru and became Little Beru's nanny. This subversive change made Oga feel very headache. Then, the demon maid Shirudi (voiced by Ito Shizuka) with a hot figure and personality came to Oga. On the one hand, he had to fight against the gangs on campus, and on the other hand, he had to take care of Little Beru with a twisted personality. Oga's thrilling and warm life as a nanny is about to begin.