[Machine Translation] Yuki Kamikura is a sleazy high school detective. He is said to have no unsolvable mysteries, but he has a secret past. He always has an "old cell phone" in his pocket, which is out of contract, and he never lets go of it. Inside it was a recorded answering machine message from a girl. Even after all these years, he has not been able to erase the contents of the message. It was the only unsolved case that Yuki Kamikura had ever had. And now, he confronts the case again. Miku feels a pain in her heart when she sees Yuhki, who is willing to give up everything to solve the case.... The only unsolved case of the strongest Dosu detective...? Newly written.