2 years ago, Kyoko's younger sister was murdered. When visiting her sister's grave, Kyoko accidentally ran into a narcotics agent. He told her that he knows about her sister's incident. After Kyoko came home, the criminal of that incident suddenly came into her house. Showing her the picture of that narcotics agent, he said "I'm not the criminal, this is the guy who killed your sister". Kyoko was then told the truth of the incident.