Forget Me Not Volume 1

Walking home from work one day, he gets into an accident, and a woman carries him to an ambulance. Later, at the hospital, still bleary, he receives a phone call from the woman who saved his life. This person knows intimate details about him. but he's not sure who it is. Serizawa's gentle personality has drawn lots of girls to him since his childhood, but he's far from perfect. Was it someone he loved and lost? Or perhaps someone he wronged, to whom he failed to make amends?