Toru and Mari are invited by Takemaru Abiko, the author of the game "Night of the Kamai Tachi", to his villa as a thank you for the success of the game "Night of the Kamai Tachi", which depicts a murder case at a pension "Spool" in the winter mountains. Although no murders took place at the actual shul, most of the characters in the game are the people who actually gathered there on the day of the blizzard a year and a half ago. Based on the game's faithful reproduction of the characters' personalities and behaviours, there is a strong possibility that Abiko is also someone who was present at the Spool that day, or is related to someone who was, but whose identity is unknown. Despite their doubts, Toru and his friends arrive at the isolated island of Mikazuki.