Plot
The story begins on October 4, 1986, at Rokkenjima (六軒島), a private island where the wealthy Ushiromiya family have gathered to discuss the division of assets belonging to the ailing family head, Kinzo.[2] Returning after a six-year absence, Kinzo's grandson Battler becomes reacquainted with the legend of the "Golden Witch" Beatrice, who supposedly gave Kinzo ten tons of gold to restore his financially crippled family in the past. Beside her portrait is a riddle-like epitaph, which is believed to grant the rumored gold and the succession of the headship to the solver. A typhoon traps the eighteen people on the island, and occult-like murders occur in accordance with the epitaph, often in ways that seem impossible for a human.
At the end of the first episode, the witch Beatrice seemingly kills everyone. In the credits it's revealed that story up this point was just a retelling of a message bottle found years after the massacre. Refusing to acknowledge the existence of magic, Battler is seemingly sent to the parallel dimension of Purgatorio, from which events on Rokkenjima can be seen as a "game board". There he meets Beatrice and faces her in the games of logic, tasked to explain murders with human tricks.
Subsequent episodes show events on Rokkenjima arranged in various different ways each time, while Battler discusses them with Beatrice and other magical entities in Purgatorio. Battler uses various logical weapons to oppose Beatrice, such as red text, in which only truth can be written, or blue text, which is considered true until refuted by red. The story also shows the real world 12 years later, where the only survivor is Eva Ushiromiya, Battler's aunt. Eva adopts Battler's sister, Ange, who did not attend the conference due to illness. Ange, who has a hateful relationship with Eva and is bullied by her classmates, refuses to accept the death of her family and tries to reach the truth on her own. Over the course of the story, Battler and Ange come to understand magic as an adornment of reality with fantasy, used by several individuals as a coping mechanism for their harsh life situations.
Battler is at first in conflict with Beatrice, despising her for the suffering inflicted upon the inhabitants of Rokkenjima throughout her games. As the story progresses, Beatrice suggests that the massacre on Rokkenjima was caused by a supposed "sin" of Battler's, which he does not recall. As a result of Battler's lack of recollection, Beatrice gives up on her games and enters a near-death state of apathy. With Beatrice no longer hosting games, other characters serve as Game Masters for the following episodes, beginning with the witch Lambdadelta in Episode 5. In this episode, the witch Bernkastel introduces a new character to the game board named Furudo Erika, a detective who seeks to solve the mystery of Rokkenjima. As this game progresses, Erika presents her supposed solution to the mystery, blaming the crimes on Natsuhi. Battler, believing in Natsuhi's innocence and unhappy with Erika's disregard for the feelings of others, opposes Erika. Upon being cornered by Erika's arguments, Battler comes to understand the truth of the Rokkenjima massacre, killing Beatrice. Knowing the truth allows Battler to defeat Erika's flawed solution, allowing him to ascend to the position of Sorcerer and Game Master.
As Game Master, Battler conducts the events of Episode 6 to prove to Lambdadelta and Bernkastel that he understands the truth of the mystery. However, the narrative he attempts to present throughout the episode is circumvented by Erika, forcing him into a "logic error," trapping his consciousness in a locked room until the error is solved or he accepts defeat. Meanwhile, a duel is conducted by Shannon and Kanon to determine which will be allowed to pursue their love, killing the other. Kanon is ultimately defeated, and through his sacrifice Battler's logic error is solved, freeing the latter. Beatrice is resurrected and joins Battler in defeating Erika.
In episode 7, Bernkastel summons detective Willard H. Wright to solve truth about Beatrice's identity. He deduces that she is Kinzo's illegitimate child, playing the roles of two servants, Shannon and Kanon. The child was born after Kinzo raped the secret daughter of his long-dead mistress. Kinzo handed the child to his eldest son's wife, Natsuhi, who had been unable to get pregnant. In an alternate world, Natsuhi accepts the child, resulting in them joining the family as Ushiromiya Lion. Willard and Lion are attacked by Bernkastel but manage to escape her clutches.
Episode 8 is another game hosted by Battler, this time as an attempt to convince Ange that understanding the full truth of the massacre is an unnecessary pursuit. However, Ange is convinced by Bernkastel to read the book containing the true events that happened on Rokkenjima, causing her to despair. The inhabitants of Rokkenjima save Ange and ultimately assist her in stopping the author Hachijo Tohya from publishing Eva's diary, supposedly containing the full truth, in the real world. In the future, Ange's suicide is prevented and she goes on to become an author. Ange meets Hachijo Tohya, who is revealed to be Battler, having survived the massacre but lost his memories, effectively being a different person. Ange takes Tohya to the orphanage she sponsors, carrying on the legacy of the magic taught to her by Maria.
