A bright girl who gets dumped by her boyfriend just before the trip they should have gone to together. She went off by herself, and there, meets a Japanese boy with whom she has a one-night-stand. She returns to Japan without even knowing his name. But there, she reunites with the boy at her father's funeral : he's her younger brother which she hadn't seen since they were kids...

Usually obedient by nature, she has a hard time dealing with her guilt upon acting against her morality, and against her mother, for whom she has always been "a good and responsible daughter".