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.

Now that Saku realizes she's in love with Haruki, she finds her heart racing for a new reason every day--until Haruki and Kotono start pretending to be a couple to protect Kotono from her ex-boyfriend. Then the blunt-speaking Iryu gets involved in Saku's life, causing even more trouble!