You are a private detective who resigned from the police force. Your childhood friend and first love, Aiko, has reappeared after many years. She works as a police officer in the Homicide Investigation Unit of the Akasaka Police Station. Just like you used to do... Your paths crossed again with a strange murder case.

You and Aiko were childhood friends. When you confessed your feelings to her in high school and Aiko thought you were joking and laughed out loud, your friendship began to break down and you haven't seen each other for many years. While you were advancing in your career with outstanding success as a police officer, you were forced to resign after you uncovered the connection of the son of a member of parliament with illegal organizations, and then you continued your life as a private detective. You attract attention with your skills. The COO of a Chinese real estate company was murdered in Akasaka and his family hired you to look into the case. On one of the days you are working on the case, one of your fellow Inspector Yamamoto Kenji calls you to the police station and asks for your opinion on the case. On your way out of the police station, a female police officer in a hurry bumps into you and falls to the ground. when you reach out to help her, she looks at you and you realize that it's Aiko, whom you haven't seen in years.