His girlfriend's best friend, who he shouldn't touch, is too erotic, so he gives in to temptation and ends up having sex with her! His girlfriend, who he lives with, is going on a family trip for a week, so he's going to be alone for the first time in a while. However, her friend Kanna came to a drinking party he hosted before she left, and while she was drunk and sleeping, they suddenly became close. When she went on a trip, Kanna wanted to come over, so he and his girlfriend's best friend started living together and having sex every day for a week until she returned...