Tokyo Metropolitan Police Department

The Tokyo Metropolitan Police Department is the central investigative institution in the novel’s Tokyo murder case, but its reach extends well beyond the city. Through its homicide division, detectives pursue the identities of Michiko Oshitani and Mutsuo Koshikawa, trace connections to Shiga and Sendai, and test the histories concealed behind assumed names. The department’s authority supplies the investigation with structure and resources; its discoveries, however, depend on patient cross-checking of records, testimony, and physical evidence.

Identity and Investigative Role

The department is identified in the narrative through its homicide division, where Kyoichiro Kaga and Shuhei Matsumiya serve as detectives. When Kaga first visits Yasuyo Miyamoto in Sendai, his card identifies him with the division. His appearance and professional courtesy make a memorable first impression, but the card also establishes the institutional link between a local encounter and a Tokyo investigation. Years later, a newspaper reference to the Tokyo Metropolitan Police, Homicide Division prompts Miyamoto to think of Kaga again, showing how the department’s public name can evoke a particular investigator and an earlier case.

The homicide division’s work is organized through superiors, assignments, and reports. After Michiko Oshitani’s identity is confirmed, Squad Leader Kobayashi orders Matsumiya and Sakagami to travel to Shiga Prefecture. Their task is to visit Oshitani’s former workplace and establish her friendships, relationships, and any links to people in Tokyo. Kobayashi directs them to report discoveries immediately and offers additional support if needed. The assignment makes the department’s investigative method concrete: a Tokyo murder is not treated as a matter confined to the scene, but as a network of connections to be pursued through regional inquiry.

Cross-Jurisdictional Investigation

The investigation relies on cooperation beyond the department. At Kobayashi’s direction, Matsumiya and Sakagami work in Shiga, while the Tokyo task force requests assistance from the Shiga Prefectural Police to find Naemura, the former homeroom teacher of Oshitani and Hiromi Asai. The response identifies Naemura as a suitable missing person: his residence certificate at his last known address had been canceled by the authorities fifteen years earlier, and no one knew what had happened to him. That information helps explain why the Tokyo detectives are sent to Shiga quickly. The department’s casework therefore advances through both its own field investigations and formal requests to local police.

The inquiry also crosses into Sendai and the histories of people who have lived under uncertain identities. Investigators find that Koshikawa’s apartment contains no ordinary personal identifiers, and the address he supplied when moving to Tokyo—Maebashi in Gunma Prefecture—leads nowhere. Detectives suspect the address is false. To test whether Koshikawa himself may be dead, they collect DNA-bearing items from the apartment, including a toothbrush, a safety razor, and an old towel, and compare the samples with unidentified people found dead nationwide. This procedure reflects the department’s need to distinguish a person’s recorded or assumed identity from biological evidence that can persist after records have been erased.

A separate forensic comparison gives the case a firmer link between identities. Fingerprints recovered from a timetable match prints from Koshikawa’s apartment, establishing that Koshikawa and the man known in Sendai as Shunichi Watabe were the same person. The number and distribution of the prints indicate that Watabe, rather than Kaga’s mother, had used the timetable most. The finding is significant not merely as a name match: it gives investigators a way to reassess the histories and relationships attached to both identities.

Evidence, Records, and Public Information

The department’s investigation combines evidence that carries different kinds of authority. Fingerprints and DNA can establish biological or physical links, while residence certificates, newspaper reports, and witness recollections provide records whose limitations must also be considered. In investigating Hiromi Asai’s past, Kaga notices that the account of her father Tadao Asai’s supposed suicide is preserved in the files of Biwa Gakuen Orphanage but lacks confirmation in official records. The absence of a reliable official trail, together with classmates’ lack of memory of the event, leads him to question whether the death occurred as reported. He finds a Hokuriku Daily article describing a body identified thirty years earlier through fingerprints on luggage and visual identification by Tadao’s daughter. The old report supplies a route into the case, but it does not identify the person who actually died; that question remains unresolved in the available account.

Publicity and media circulation are also part of the department’s information environment. A kendo magazine had interviewed Kaga after he won the national police championships in judo and kendo. Although the magazine did not print his home address, he had given it to the publisher so that a complimentary copy could be sent to him. Later, when someone’s ability to contact him at home becomes relevant, Kaga asks Mogi to make inquiries without alerting the publisher that the matter is connected to a murder. The inquiry is framed as a survey of the effect of police public-relations outreach, and Mogi uses the magazine article to ask Machiko Yoneoka who had requested Kaga’s contact details. The episode shows how an ordinary publicity arrangement can become an investigative lead—and why detectives may need to control how they present their questions to preserve the value of a source.

The department itself also appears in the public sphere as a source of news. Miyamoto reads about a woman found dead in a Tokyo apartment and wonders whether Kaga is involved, because the wording in the article recalls the homicide division. In another instance, Hiromi Asai sees news that a decomposed corpse in a deteriorating apartment has been identified and suspects that the report concerns Oshitani. These notices provide partial information rather than a complete account, prompting personal reactions while the formal investigation continues. The contrast between a public report and the detectives’ fuller, still-developing inquiry underscores how little a headline can establish about identity or connection.

Authority, Procedure, and Professional Conduct

The department’s authority is made visible through badges, business cards, and the language of formal inquiry. When Matsumiya introduces himself to Takeo Suwa, he identifies himself as an inspector in the Tokyo Metropolitan Police Homicide Division. Suwa says another detective has already asked about Oshitani’s murder and about what he knew of Asai’s earlier life in Shiga. Matsumiya then presents a sketch of Koshikawa, also known as Watabe, for Suwa to examine. The meeting shows investigation as a sequence of contacts: one detective’s visit is followed by another, each using a different question or piece of evidence to build the record.

In a separate inquiry, Matsumiya identifies himself with the Tokyo Metropolitan Police Department when approaching an elderly former worker at the Hamaoka and Onagawa nuclear power stations. He does not immediately announce his affiliation at the door, wishing to avoid drawing the neighbors’ attention; once the door opens, he presents his badge and explains that he needs help with an investigation. This exchange illustrates the practical balance between recognizable authority and discretion. The badge establishes who is asking, while the careful approach allows the detective to begin questioning without making the visit conspicuous.

Kaga’s own conduct is similarly shaped by professional restraint. After the magazine feature gives him reason to wonder whether his address was passed on, he has considered asking the publisher directly but avoids using his rank to pursue a personal matter. When he finally seeks help, he does not want a murder inquiry to make the publisher less forthcoming. His reluctance to exploit his position and his attention to how a question may affect the answer distinguish procedural caution from mere formality: the department’s investigative effectiveness depends in part on detectives knowing when to invoke their authority and when to keep it in the background.

Development and Narrative Significance

The department’s role changes as the investigation gathers evidence. Early work establishes Oshitani’s identity through fingerprint and DNA results, directs detectives toward her former workplace, and seeks a missing teacher who may connect the two women’s pasts. Later work links Koshikawa to Watabe through fingerprints, revisits the uncertain record of Tadao Asai’s death, and awaits DNA testing to determine whether Hiromi Asai is Koshikawa’s daughter. The sequence moves from identifying a victim to testing the identities and relationships that could explain the case. The department does not resolve every uncertainty at once: the identity of the body involved in Tadao’s alleged death remains unknown, and a test result is still pending at the point described.

The institution also frames Kaga’s movement through the story. By the end, Matsumiya reports that Kaga is transferring to Tokyo Metropolitan Police Department headquarters and rejoining the homicide division, though in a different section from Matsumiya. The transfer closes a structural circle: Kaga, first encountered in Sendai as a homicide detective who had come to visit Miyamoto, is returning to the department’s headquarters and to homicide work. Across the novel, the department functions not as an omniscient authority but as a network of investigators and procedures—capable of coordinating across regions, yet dependent on records that may be false, memories that may fail, and evidence whose meaning emerges only through comparison.