On the secluded island of Rokkenjima, owned by the rich and powerful Ushiromiya family, mysterious murders begin to occur as outlined on the epitaph of the Golden Witch Beatrice, whose existence has been continually denied by Battler Ushiromiya.
When Beatrice defaults a win against Battler, she loses the will to continue and withdraws. As Battler waits for her to awaken, the witches Bernkastel and Lambdadelta wreck havoc upon the game board and the fates of those on Rokkenjima. When Battler re-enters the game to take the game board back for Beatrice, he discovers the circumstances have changed.
In 1986, detective Erika Furudo has joined the inhabitants of Rokkenjima, approaching the murders from a “mystery” perspective in contrast to Battler’s approach of “anti-fantasy” and denying magic. As Erika’s investigation begins, the consequences of Natsuhi Ushiromiya’s past actions regarding an offer from the family head, Kinzo, surface.