His wife died in a car accident. But months before she died, she donated her blood to another girl. He ran away hoping to start anew but a year after his wife's death, he decided to come back and look for the girl who has his wife's blood. He believes that a part of his wife's still alive in her. She doesn't believe in Ketsuekigata (personality through blood types). But why does her heart awkwardly beats everytime he see that man? It's as if someone else's heart is beating