Miyu-chan was hurt by her boyfriend's comment, "They're surprisingly small," as he has a fetish for large breasts. Following her mother's advice, she tries an at-home breast enhancement spa treatment, only to find herself assigned to a suspicious male therapist. Despite her apprehension, she accepts the treatment, which gradually turns into a lewd massage... She begins to feel her breasts grow, and despite her embarrassment, she continues to go. Eventually, her nipples are relentlessly stimulated, becoming so sensitive that she arches her back and orgasms from nipple stimulation. Her reason crumbles, and finally...