Ten Kara no Okurimono

Hikari befriends a gentle boy named Seiji who suffers from a weak heart while she was hospitalized. She begins to fall for Tsukina, Seiji's twin brother, who has always sacrificed for his sick brother. Tsukina believes that Seiji is in love with Hikari and steps back from the two, much to Hikari's dismay. What will happen to the three?