It's summertime, and the setting is their husbands' parents' house. With their husbands out on the golf course and their mother-in-law constantly nagging them, stepsisters Riisa and Tsubomi feel adrift and isolated. A different kind of heat begins to build between them, a magnetic pull that draws them closer together. In the Japanese-style room, in the bath, out on the veranda... their beautiful bodies intertwine in passionate, sweaty lesbian sex. It's a secret relationship, a fleeting affair just for the two of them, to last for one summer only.