My girlfriend's best friend, who I would never let her touch, is so erotic that I give in to temptation and have sex with her! - A man who was supposed to be alone for the first time in a while because the girlfriend he lives with has to leave her room for a week on a family trip. - However, he suddenly approaches Sumire, a female friend of hers who came to a drinking party she held before her departure, and she got drunk and fell asleep. - Then, when she went on a trip, Sumire contacted her and said she was coming to visit, and they started living together for a week, having sex with Sumire every day until she returned...