One day, Sawatari Kouta agrees to help his grandfather manage a mansion, which involves managing and overseeing the reception desk of the residents-only gym. However, there are only a few other occasional users, with just one person using it regularly. He is initially frustrated about wasting two weeks for such a small task. But then Kouta meets that regular — a smoking hot woman with a sexy, erotic vibe. She's rocking tight sportswear that clings to her massive boobs and highlights her hard nipples, with her panty line teasingly visible. Thus, his unforgettable summer begins.