The harmonious intersection of the Violets and the Goldies set to be done at the Kogetsukan hotel. Chaldea's master, Ritsuka Fujimaru, finds themselves sucked into this whirlpool, connected to the character Rikka in the center of this mystery. Thus begins the investigation into the serial murders that occur in this isolated mansion built on an island, with different characters dressed up as similar faces, notwithstanding the help of a world-famous detective and the king of crime.