Beginning on New Year’s Eve in the year 2021, a series of murders occur one after another. The murders involve a family member who possesses a special ability called “personality shifting”. On New Year’s Eve, Hiroko’s “personality shift” ability is triggered by the murder of her husband. Her consciousness is transferred into that of her husband, the murderer. In this state, she summons her daughter Asahi, who is unaware of what is going on, and turns against her “father who murdered her mother,” and kills her father (who is actually her mother, Hiroko). Then, Hiroko’s consciousness enters her daughter’s body. Meanwhile, Takao, a detective pursuing a murder case, is pushed off a bridge by someone, activating his personality transfer ability. He transfers into the body of his daughter, Rinka, who seems to have been present at the scene. Hiroko and Takao are members of the same family with the same ability. The two pursue two mysteries: their own special abilities and the murder case. One old woman holds the key to all the mysteries. A masterpiece of “special setting” mystery created by the author who won the “2023 Japan Mystery Writers Association Award for Short Stories”.