椿屋敷の亡霊

The time is the early Showa era.
A letter arrived at the Mikage office. A series of murders that occurred in the Sakaki and Hirunuma families. The investigation comes to an end without the truth being solved. A request arrives to uncover the truth of the case. However, the sender is a person named Hazuki Hirunuma, who should have died 15 years ago. Mystery begets mystery, and Mikage Fukuro takes on the challenge as an armchair detective.