At a class reunion more than a decade after graduation, Sayu cannot stop thinking about Keiichi, the first boyfriend she ever had—and he feels the same. Though both confirm that they are married, they still exchange contact details. Once too shy even to hold hands, they are now grown adults, and Keiichi becomes obsessed with Sayu’s mature, alluring body. Lonely from her husband’s neglect, she accepts him, and the former lovers have sex again and again as their affair deepens.