"I have always felt guilty for one of my students because I made a serious mistake ten years ago. Recently, I finally learned the truth about the incident that made me bear the responsibility for ten years." The deceased sent such an email to his brother, but before he could tell others the truth, the deceased was killed. The chess pieces were scattered all over the floor at the crime scene. If you look carefully, you can see that a few are missing. Did the deceased leave any death information? Who took the chess pieces? What is the relationship between the death of the deceased and what happened ten years ago? What is the truth of the matter? Even if the information people receive is true, it may not be what they think it is. It may just be due to misunderstanding.