ayumi is a student who is always thinking about sex but is shy and unpopular. One day, he sees ranka, a black gal rumored to be a slut, masturbating and giving head to a man in the stairwell of the same apartment building, and accidentally takes a photo with his smartphone. It seems that he was caught taking pictures, and the next day he was ambushed in the stairwell and taken to ranka's room.
