Within the Tsukishiro mansion lay a secret unknown to anyone. Deep inside the vast mansion lived Chizuru Tsukishiro, a sickly girl who knew nothing of the outside world. And you, who visited her room almost every day. Taken in by the Tsukishiro family and raised as Chizuru's substitute, you made it a daily routine to tell Chizuru about the scenery she saw outside and the changing seasons. In that closed world, it was Chizuru's only joy. That is why, before she knew it, Chizuru began to wish she would never have to give you up to anyone.

On one such spring day, at a social event between a prestigious academy and a girls' school, you met Reiji Mikage, the heir of the Mikage family. While everyone else was captivated by family status and beauty, Reiji alone was entranced by the sight of you, who smiled somewhat lonely, without a trace of pride in the admiration.

Unable to forget that feeling, Reiji visited the girls' school a few weeks later to see you once more.