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's feelings for Haruki are more powerful than ever. After opening up to Kotono, the misunderstanding between the two friends has been resolved. But when Saku finds out that Iryu might be the guardian angel who saved her years ago, the relationships among these friends begin to change...