Ritsu was abandoned by his mother Reiko when he was little, so now he belongs in the lower social strata. One day, Ritsu gets involved in a case and his head is severely injured, so he can die at anytime. Convinced she abandoned him due to poverty, Ritsu attempts to find his mother and be good to her before his death. But when he learns that she is leading a happy life instead, with her pianist son Satoru, he decides to take revenge on his mother. Ritsu then meets Rinka, a girl whom he happened to help in the past, and discovers she is Satoru's childhood friend.