Childhood friends Yuma Okazaki and Hotaru Mizushina are high school students, leading happy lives with their respective boyfriends Takeda and Fujiwara. Their bond seems unbreakable as they play at school and go on group dates together. During one of their outings, however, Hotaru surprises everyone by stroking Yuma's thighs while Takeda and Fujiwara are distracted. Yuma is taken aback by this unexpected action and retreats awkwardly to the bathroom, followed closely by Hotaru. Alone and secluded, Hotaru corners Yuma in a locked cubicle and whispers, "You'll be more comfortable with a guy; I'll help you practice."