Asakusabashi Bridge is a bridge on the Kanda River and one of twelve Nihonbashi-area crossings recorded against the months of the year in two matching lists central to the investigation. Its importance is not simply geographical: the bridge is the February entry, the place where Kaga and Shuhei Matsumiya begin tracing the route, and a point of departure from which the pattern becomes a journey through the city.

Setting and Place in the Bridge List

The list assigns Asakusabashi Bridge to February, between Yanagibashi Bridge in January and Saemonbashi Bridge in March. The other entries extend across the year and include Tokiwabashi Bridge, Ichikokubashi Bridge, Nihonbashi Bridge, and Toyomibashi Bridge. The bridges are identified as belonging to the Nihonbashi area, with the route following crossings on either the Nihonbashi River or the Kanda River. Asakusabashi Bridge thus sits within a deliberately ordered sequence rather than appearing as an isolated place-name.

The month labels initially invite a straightforward explanation: perhaps each refers to the month when the corresponding bridge opened. Kaga and Matsumiya test that idea against construction dates. Yanagibashi Bridge was completed in July 1929, Asakusabashi Bridge in June 1929, and Saemonbashi Bridge in May 1930. Those dates do not match the list’s January, February, and March sequence, leaving the purpose of the monthly arrangement unresolved at this point in the investigation.

A Clue Preserved in Two Lists

The detectives first encounter the sequence as annotations written on every page of Mutsuo Koshikawa’s calendar. Asakusabashi Bridge appears on February’s page. The markings are not confined to that month: all twelve pages carry a bridge name, and investigators note that the complete series concerns bridges in the Nihonbashi area. A search team considers whether the entries might refer to events Koshikawa attended on the bridges, but finds no supporting information. The annotations remain a question rather than an explanation.

A second copy of the same sequence comes from a separate source. Kaga has found a sheet of paper in his late mother’s apartment, though he is careful to say that its presence there does not establish that it belonged to her. He also notes that the handwriting is not hers. When he shows Matsumiya the list, its places and month assignments match Koshikawa’s calendar exactly, including Asakusabashi Bridge in February. The match prompts Kaga to ask the task force to arrange handwriting analysis, turning the repeated list into a possible link between otherwise separate strands of the case.

Kaga tells his superiors that his mother had a long-term relationship with Shunichi Watabe, and suspects Watabe may have written the list. He has been unable to establish who Watabe was or what the note meant. At this stage, Asakusabashi Bridge belongs to a coded-looking pattern whose provenance is uncertain: it is present in Koshikawa’s calendar and in a note found among Kaga’s mother’s effects, but the evidence has not yet explained why either source records the route.

The Route Begins at Asakusabashi

Kaga eventually proposes following the bridge sequence by boat. He explains that the listed crossings lie on the Nihonbashi and Kanda rivers and says that he plans to travel along both waterways. When Matsumiya asks where the boat departs, Kaga names Asakusabashi Bridge. The February entry is therefore also the practical beginning of their attempt to understand the order by moving through the places it names.

Matsumiya hurries to the bridge and reaches the landing stage on the Kanda River a few minutes before three. Kaga is waiting at the top of the stairs; he tells Matsumiya that they were about to leave. This meeting gives the list a physical setting and a timetable, but not yet a solution. From the boat, Matsumiya reads the months and bridges from his notes as they approach Tokiwabashi Bridge, asking whether the months might mark opening dates. Kaga checks the construction records, and their comparison rules out that initial theory.

Investigative Significance

The bridge’s narrative significance comes from its repeated appearance in a chain of evidence. As a calendar annotation, it contributes to the pattern linked to Koshikawa; as an item on the note found in Kaga’s mother’s apartment, it helps establish that the two lists are identical; and as the boat’s departure point, it becomes part of the detectives’ effort to test the pattern directly. These roles connect a mundane city route to questions about the note’s author and Watabe’s identity.

The investigation later reconsiders its assumptions about the person called Watabe. Kaga reasons that Watabe had been connected to Hiromi Asai for at least ten years, had little apparent connection to other people, may have received financial support from her, was of an age consistent with being her father, and knew Michiko Oshitani. He concludes that Watabe was likely Hiromi’s father, Tadao Asai. That deduction places the unexplained list within a wider concealed family history, although the supplied evidence does not establish the meaning of the bridge sequence itself. Asakusabashi Bridge remains important as a precise, recurring marker in the route through which the detectives pursue that history.