Kurumi learns that her beloved first boyfriend prefers big breasts, so she asks her masseuse stepfather to help enlarge hers. Using some very questionable ideas about the Spence gland, he massages her small breasts and plays relentlessly with her nipples until her petite adult body becomes hypersensitive and convulses through repeated orgasms. The overwhelming pleasure leads to bareback sex and multiple creampies—all supposedly to make her boyfriend happy.