Today the students of "Tokyo metropolitan government-run magic school" will be assigned their partner, familiar spirits. In front of a student, Kouji Yuno, who uses black magic, an incubus, Harlem, appears. Harlem is very cute but helpless. Yuno is not happy but relents. They spend their lovely days with Yuno's good-natured classmate girls, Fuyuno with a snake and Midori with a cat

A lesson of changing familiar spirit into human. Harlem's real age is revealed.

Another classmate of Yuno's, Tsukasa Takagi, is released from hospital. Takagi's familiar spirit is an incubus too, Meramie. She is excellent and has it in for Harlem. Meramie makes a pass at Yuno, then it comes about that Harlem will have a showdown with Meramie over Yuno. It seems he is losing the game but Yuno hits on a secret good plan...

A regular-examination season comes. Yuno is poor at Math, so he should buckle down to study with Midori alone. He treats Harlem as a nuisance...