Matsuki is a journalist who works as the editor of an aviation magazine. He is an old schoolmate of Takao Yazawa, the former Japan Air Self-Defense Force pilot and protagonist of the story. Motivated by a professional interest in aviation and a personal connection to Yazawa, Matsuki contacts Yazawa after learning that a Phantom jet fighter—a type of aircraft that should only be in service with Japanese forces—has been sighted in the conflict in El Salvador. He asks Yazawa to help investigate the appearance of this Phantom, setting the main plot in motion. Matsuki is persistent and dedicated to uncovering the truth behind the international arms conspiracy surrounding the jet. As the investigation deepens, he becomes a target of the shadowy organization involved; he is eventually captured and imprisoned by the conspirators. Matsuki shares a close, trusting bond with Yazawa, grounded in their shared history and mutual respect. Throughout the story, his role shifts from an instigating contact to a victim who requires rescue. His fate is tied to the dangers of the conspiracy, and he ultimately dies during the course of the events, a loss that deeply affects Yazawa. Matsuki does not possess any special combat or supernatural abilities; his strengths lie in his journalistic skills, his knowledge of military aviation, and his willingness to pursue the truth despite considerable risk.