Synopsis
One morning, a man awaits two Tokyo Metropolitan Police special investigators in their tiny office. He is Takeru Kanbe (Mitsuhiro Oikawa), once an investigator himself and now attached to the secretariat of the National Police Agency Director-General. Inspector Ukyo Sugishita (Yutaka Mizutani), greets his former partner fondly, while his current sidekick Toru Kai (Hiroki Narimiya) meets him for the first time. Kanbe has come to see them regarding a tiny newspaper article with a headline that says “Man Kicked by Horse Dies.” The incident happened on the little-known island of Hououjima, located 300 kilometers from Tokyo in the Pacific Ocean, and appears to be nothing but a mere accident. Kanbe has been ordered by NPA Deputy Commissioner-General Mineaki Kai (Koji Ishizaka) to dispatch Sugishita and Kai to the island to get to the bottom of incessant rumors about what is actually going on there. “Wouldn't you like to investigate them for yourself?”, he asks. After stirring Sugishita and Kai's curiosity, Kanbe places two airline tickets to the island of Hachijojima (a transfer point on the journey to Hououjima) on a desk and leaves their office. Despite their reluctance, the special investigators board a boat from Hachijojima bound for Hououjima. The island is privately owned by entrepreneur Michihiko Wakasa (Shin Takuma), and is the location of a base used by a militia comprised of former Japan Self-Defense Forces troops who train and live there together. Their leader Tsukasa Kamuro (Tsuyoshi Ihara) and his officer Shimako Takano (Yumiko Shaku) guide Sugishita and Kai to the place where the accident occurred. The militia members are outwardly compliant, but the investigators are clearly unwelcome visitors. The man who died in the accident was a company employee and JSDF reserve who had come to the island temporarily to take part in training maneuvers. Although the accident investigation was only a cover story to conceal the police's true objective, Sugishita gives full reign to his characteristic skepticism and insight. His suspicions deepen that is not a case of accidental death but instead a murder, and secretly makes contact for forensic technician Mamoru Yonezawa (Seiji Rokkaku) in an attempt to secure evidence. Meanwhile, forces are at work within the Tokyo Metropolitan Police. DCG Kai, Toru's father, pulls strings to send detectives Kenichi Itami (Kazuhisa Kawahara), Shinsuke Miura (Ryosuke Otani), and Kenji Serizawa (Takashi Yamanaka) to the island with orders to bring the special investigators back to Tokyo. Sugishita, Kai, the three detectives, and forensic technician Yonezawa are reunited on the island, and discover decisive evidence that holds the key to the truth behind the accident. However, on their way back to their temporary quarters, they are captured by a special forces unit clad in camouflage gear. Sugishita and Kai realize that the tactics used in the highly calculated attack are completely different to those of the militia... What is the true identity of their assailants, and what is the island's secret? This remote location, completely isolated from the outside world, becomes a massive enclosure as the accident investigation transforms into a murder case, and a vast, baffling mystery unfolds that implicates the Defense Ministry and other powerful forces within the government... Discover the shocking truth behind the most thrillingly intricate mystery in the history of the “AIBOU” franchise! A mystery within a massive enclosure. An accidental death that is much more than it seems...