Self proclaimed "Hard-Boiled" person, Asahina Jinta is recommended by his former employer to work in a private investigative agency. On the first day at work, his bike got swerved by a car and to his surprise, the car owner is a beautiful girl, a detective called Shouko and she has a baby with her. He's shocked, this is different from what he imagine the detective life to be.

In the office, things get worse when Asahina found out that the life here is not that different from working in a corporate organization and his main job is to babysitting shouko's baby.

However, Asahina won't give up easily. When the phone rang, he rushed in and took the phone before the operator pick it up and soon the first investigative case in his life begins. Asahina just had a first glimp of the dirt of human's dark side.