Desperate to lose his virginity, Sou makes a bargain by summoning a devil named Kogure from the underworld to help with the deed. However, when Sou discovers that Kogure is a boy rather than a girl, he flees the underworld. Thinking that the ordeal is over, Sou returns home only to find that Kogure is there - and determined to stay - until the bargain that they made is satisfied! Unwilling to give up his virginity, Sou tries to figure out a way to nullify the agreement, but finds himself blocked by Kogure. Kogure insinuates himself into Sou's life and is willing to do whatever it takes to win Sou over. How will Sou handle have a devil in his life?