Total Reasoning: the Last Murderer

10 Years ago, Bao Na, a member of E University's reasoning club, was killed in a reasoning salon. The scene of the murder was a closed secret room. The remaining seven members who participated in the event did not remember what happened. Everyone was suspected. However, due to insufficient evidence, the case became an unsolved case. The seven members also graduated successfully and went their separate ways. Ten years later, the seven people reunited again. Seven people who received invitations one after another went to this secret feast. Seven people were once again locked in a confined space. The items that pointed to everyone's motive for committing the crime 10 years ago reappeared in front of everyone, forcing everyone to take off their masks. The mysterious man who brings everyone together is hidden among the seven people. At the same time, they need to complete the task assigned by the mysterious man within seven days and find the real murderer hidden among them. Seven people and seven stories, who is lying?