Nihonbashi Police Station

The Nihonbashi Police Station is a local police organization involved in the investigation linking a calendar of Tokyo bridges to a murder and to Kyoichiro Kaga’s family history. Its work ranges from neighborhood canvassing and examining photographs to pursuing leads through the station’s own kendo activities, making it both an investigative base and a source of connections that help the case take shape.

Role in the Investigation

Alongside his colleagues from the Nihonbashi Police Station, Kaga investigated the significance of a list of bridge names that matched the dates on Mutsuo Koshikawa’s calendar. The bridges lay along the Nihonbashi and Kanda rivers, so the inquiry had a concrete local geography as well as a personal dimension: Kaga’s mother had a long-term relationship with Shunichi Watabe, and Kaga suspected Watabe might have written the list. He admitted he knew almost nothing about Watabe and had been unable to work out what the note meant.

The investigation initially made little headway. Kaga and the other officers showed a sketch around the neighborhood but received no useful information. He planned another circuit, this time by boat along the two rivers and their bridges, pursuing the route suggested by the calendar even though he had little hope that the canvass would succeed. The episode shows the station’s inquiry moving between documentary clues and direct contact with the places named in them.

Local Contacts and Leads

The station also appears in a separate connection that helped bring Hiromi Kadokura into the inquiry. Kadokura explained that she had found a kendo workshop organized by the Nihonbashi Police Station through an online search, then approached Kaga to teach a small group of children at Hamacho Park’s sports center. Kaga noticed that the location was not especially convenient to her office or apartment and asked why she had chosen it. Kadokura could offer no particular explanation beyond having come across the workshop online. The exchange gave Kaga a reason to examine her movements without establishing, by itself, why she had made that choice.

The station’s bridge-washing photographs supplied another investigative lead. When asked whether anything unusual had happened in the year a photograph showed Kadokura, Kaga explained that the police were checking whether the ceremony might connect to an incident under investigation. The photograph was the only one in the set featuring an actress, which made it stand out for review; the photographer recalled no special circumstances and said Kadokura had simply happened to be there. The station’s officers thus treated an ordinary public image as a possible link, while keeping the limits of what the photograph established in view.

Institutional Connections and Significance

The Nihonbashi Police Station’s kendo workshop also formed part of the wider investigation’s network of relationships and information. Kaga’s appearance in a kendo magazine followed his wins in the national police championships for judo and kendo. The magazine had his address because he supplied it so a complimentary copy could be sent, although the address was not published. Years later, he considered whether the publisher might have disclosed it, but hesitated to use his rank to pursue a personal question; he sought help discreetly because he did not want to alert the publisher to the murder investigation.

In the case itself, evidence connecting Hiromi Asai and Shunichi Watabe prompted Kaga to reassess the presumed identity of Watabe. He reasoned that their long-standing connection, the likelihood that Asai had supported Watabe financially, Watabe’s age and disappearance, and his acquaintance with Michiko Oshitani pointed toward a close personal or family relationship. Kaga proposed that Watabe was in fact Asai’s father, Tadao Asai, and that the reported death attributed to Tadao had been used to erase his identity. The station’s local contacts and investigative work sit within this broader process: individual leads do not settle the case alone, but help expose the relationships hidden behind names, records, and public appearances.