Strange House

In my work, I often encounter various mysterious incidents related to houses. But this story is unlike any other… When an old friend asked me to take a look at an unusual house plan he was about to buy, my attention was drawn to a mysterious empty space on the first floor. So, I wrote to a familiar architect, Kurihara. He immediately became interested in the unconventional layout, noting several oddities: a children's room without windows, a suspicious arrangement of rooms, and a secret passage… Kurihara proposed a crazy theory, which would have remained just that if a dismembered body without a left hand had not later been found near the house. Below, I present the entire story in chronological order. Some details are hidden to maintain confidentiality.