いけないこと、しよ？

Tobako is a strict student council president known for good conduct and for disliking boys. Then she meets Yui, a younger boy who keeps pressing close even after she says she wants nothing to do with them. He ends up learning a secret she has kept hidden for a long time. That discovery pulls the two of them into a relationship she sees as dangerous. Her carefully controlled school life starts to tilt once this insistent junior gets involved.