"I wonder if being tied up with ropes feels good?" With this shocking remark, Aoi, Kana's best friend, after witnessing her parents' bondage play, awakens a forbidden curiosity. Unable to resist, Kana seizes the excuse of bondage to approach and assault Aoi, immobilized and defenseless. Though they know that "girls shouldn't do this," the pleasure is overwhelming. Once discovered, the sensation becomes addictive, and their encounters escalate: bondage in school swimsuits, intense squirting, strap-on training sex… As they plunge deeper into SM lesbian passion, their relationship transforms into an immoral secret between schoolgirls.