Shimada Shuichi was sorting through the belongings of his recently deceased friend and found a letter without a name and address. It was a letter addressed to himself. The letter scrawled with the words "Look for me at the day and night mansion under the floor". Shimada gradually remembered something vaguely, and then went to the Kinoshima day and night mansion with his friends to find the truth. A secret room murder case? Or a Japanese ghost story?
Intention: Under the huge inheritance, friends? Money? Or... Salvation?