The bud of bittersweet first love takes bloom!. A mysterious boy comes to Saku Fujigaya’s rescue when she falls ill on a train, but he leaves before she can thank him. After this experience, Saku never ignores strangers in need of help to emulate the boy who helped her. . Saku Fujigaya would like to thank the boy who helped her, but all she has is a note signed “Ryosuke Sakura.” She discovers that a boy at her high school, Haruki Sakura, has an older brother named Ryosuke. She asks Haruki to deliver her thank-you letter to Ryosuke, but why does he refuse?