After failing his university entrance exam and being forced to become a ronin student, Satoshi's worried parents arrange for Mitsuyo, an acquaintance who works as a private tutor, for academic support. However, Satoshi finds himself unable to concentrate on his studies, distracted by Mitsuyo's exceptionally voluptuous bust. Seeing his lack of focus, Mitsuyo proposes a deal: if he studies hard, he can touch her breasts freely. Spurred by her offer, Satoshi becomes highly motivated. Yet his desires gradually escalate, leading their relationship down an increasingly bizarre and unpredictable path.