Kuzumi Kentarou is a salesman and also a organ donor card owner (their organs get donated upon death). He gets mugged and almost dies but eventually regains consciousness in a hospital and sees a patient with an ailing heart, Hasegawa Kirin, who tells him that he is completely compatible with her...as a donor. (very evil and selfish of her)
Kentarou promised to give his heart to her. Kentarou lives on but he never got into college. He now works part-time in the hospital where he begs Kisaragi Ryouko, an organ transplant coordinator, “when will Kirin receive his heart?“ Maybe at the end of the story, if we will ever see it..