Reigo Island Seventeen-Victim Massacre

The Reigo Island Seventeen-Victim Massacre (囹圄島の17人虐殺 ,) is the event that led to Yukito Ayatsuji being labeled as a "Special A" grade threat.

Overview
The massacre occurred five years ago in Reigo Island, where Ayatsuji pretended to live in for quite some time. He eventually solved the crime, and the 17 people who planned the murder all died through accidents as fulfilled by his ability. Inspector Asukai also happened to be present that time.

Among the victims-cum-suspects in the massacre is Mizuki Tsujimura's mother. After her death, Tsujimura seemingly inherited the former's ability and is recruited into the Special Division for Unusual Powers, where she becomes the supervisor to Ayatsuji, the primary "suspect" to the island massacre.

The 18th murderer who is the mastermind of the incident was not found. The only information about the mastermind is that it was a male who lost the first part of his ring finger. He was not killed since he escaped when Ayatsuji came to the island. Nonetheless, he is soon called by the police as the "Engineer" based on his profession and later discovered by Ayatsuji, Tsujimura, and Asukai and his team after being caught on camera apparently responsible for an elevator crash in the Justice Ministry building.

Involved People

 * Asukai
 * Yukito Ayatsuji
 * Kubo

Trivia

 * The incident bears some nods to the real-life 's debut novel, :
 * Like the massacre in Reigo Island, the novel's murders are also set on an island, where the Decagon House is located.
 * The 17 victims were considered as prime suspects who planned murder. The novel's central characters are also suspected to committing murder, in such a way that they think they are being killed off by someone among them.
 * The 18th Reigo Island murderer apparently survived from Ayatsuji's ability after escaping Reigo Island, while the novel's primary suspect among the group also survived and left the island in the end.