One summer day, a boy named Tatsuomi Shiba arrives in the town where Riko, an eighth grader, lives. His family, who are related to the chairman of a major corporation, are welcomed by the townspeople, but Tatsuomi keeps his distance from everyone around him. Riko, who cannot leave him alone, makes memories of their summer together, and on his birthday, she promises Tatsuomi a gift and a promise. However, their happy days come to an end with the end of summer. Who is the person I fell in love with for the first time?