While their boyfriends wait outside, Hotaru Mizushina passionately kisses her childhood friend, Yuma Okazaki, in a bathroom stall. Under the pretext of practicing for their boyfriends, Hotaru continues to tease Yuma—but could she have other motives for doing so?

Despite an ongoing relationship with her boyfriend, Yuma cannot stop thinking about Hotaru ever since their kiss, and complicated circumstances between these students arise.