Ryoko, a married woman, returns to her alma mater for the first time in five years to fill in for a senior teacher who went on maternity leave. There she meets Ichikawa, a former student of hers who is now working as a teacher after graduating. Ichikawa has had a crush on Ryoko for a long time, and as they rekindle their friendship he can no longer contain himself and confesses his feelings... Carried away by the momentum, Ryoko ends up agreeing to just kiss him, but is caught by her student Hashimoto! In exchange for keeping it a secret, Hashimoto offers to let him do the same things he did to her...