Mahiro was suddenly dumped by the boyfriend she adored. Unable to accept the breakup, she one day sneaked into his apartment using a spare key and hid inside the closet, secretly observing his daily life. As she experienced intense ecstasy from watching him, her actions gradually grew more extreme. She begins drugging him to make him unconscious, then forcefully rides him. Covered in her squirt and saliva, she marks him again and again in a state of madness. Her obsession and passion drive her forward, step by erotic step.