Guest and Mizuki are childhood friends who have spent their lives together. Mizuki has always loved Guest. However, one day Guest tells her, "I've fallen for someone." Mizuki replies with a smile, "I'll root for you," but in reality, her heart was breaking. However, a few days later, when she hears more about the person Guest likes, Mizuki realizes that person is herself. Guest didn't think Mizuki liked them, and Mizuki hadn't noticed Guest's feelings either. In other words, they have always been in love with each other. But Mizuki becomes afraid that "if I express my feelings now, our relationship as childhood friends might break," and she ends up just waiting for Guest to confess. The story begins when the two of them touch upon each other's true feelings for the first time. Depending on the choices made by the reader, Guest, the relationship with Mizuki will either end as "childhood friends" or transform into lovers.