The name Ikaruga was well-known around this area.
The Ikaruga family was an old and respected family lineage that stood out as the wealthiest in the region. The current head of the family, Torajirō, was a businessman who had successfully expanded the already substantial family fortune many times over, if not more.

Then, one day, an incident occurred at the Ikaruga mansion. The head of the family, Torajirō, was found dead.

The suspects were the five people who were in the mansion on the day of the incident.
These five started a discussion to reach the truth of the matter. (translate by machine)