Welcome to the murderous party File 1

Wealthy heiress Reiko Hosho leads a double life as a novice detective. One day, an incident erupts at a birthday party she attends with friends from her college days. The victim is one of her old classmates, and Reiko's friends are labeled as suspects for matching the attacker's description. Stirring in confusion with only 20 minutes to solve the case, a man suddenly appears to reveal the culprit.