The protagonist is a student at a certain academy. Having the summer vacation scheduled soon, he made up his mind to confess his love to his classmate Shimatani Tomoka. His confession succeeded.

He wanted to fully enjoy his last summer vacation in the academy with her, but she is as serious as saying she has to spend the vacation studying for entrance exams. So they study together in his house thanks to his parents often absent from home. As they study in a locked room, they gradually get closer to each other. After thinking for a long time, he tries to even deepen the relationship, but......

The situation shows signs of change since the day. Suddenly she takes distance from him. Childhood friend's uncomfortable response to his asking. A man's shadow he can barely recognize behind the scene.

He ponders every time the summer day comes: "If I made a different choice in that time, my life should be better....."