Nishigashibashi Bridge is the June entry in a twelve-month list of Nihonbashi-area bridges that becomes a recurring clue in the investigation of Michiko Oshitani’s murder. Its significance lies less in anything discovered at the bridge itself than in the way its place in the list connects Mutsuo Koshikawa’s calendar to a matching note found among Kyoichiro Kaga’s mother’s effects, a connection whose meaning remains unresolved in the material surrounding the bridge.

Place in the Twelve-Bridge List

The list assigns one bridge to each month: Yanagibashi Bridge to January, Asakusabashi Bridge to February, Saemonbashi Bridge to March, Tokiwabashi Bridge to April, Ichikokubashi Bridge to May, Nishigashibashi Bridge to June, Nihonbashi Bridge to July, Edobashi Bridge to August, Yoroibashi Bridge to September, Kayababashi Bridge to October, Minatobashi Bridge to November, and Toyomibashi Bridge to December. The same sequence appears as annotations across the pages of Mutsuo Koshikawa’s calendar and on a separate sheet Kyoichiro Kaga found in his mother’s apartment. The handwriting on Kaga’s note was not his mother’s, and its ownership was uncertain. Kaga told his colleagues that his mother had had a long-term relationship with Shunichi Watabe and suspected Watabe might have written the list, though he knew little about the man and had not been able to work out what the note meant.

The calendar’s annotations had already drawn the attention of the search team. Investigators considered whether they recorded events held on the bridges that Koshikawa had attended, but found no confirming information. The repeated entries thus served first as a pattern to recognize rather than an explanation: the same bridge names appeared in two separate objects, but the calendar and note did not disclose why they had been written down.

The June Entry on the Investigation Route

During a visit to the bridges, Shuhei Matsumiya looked for something at Nishigashibashi Bridge that might connect it with June. The scene offered no obvious lead: office buildings stood on either side, and he could identify nothing that explained the month’s designation. After passing Nishigashibashi Bridge, he and his companion reached Nihonbashi Bridge, the next stop in the sequence. Matsumiya wondered whether July’s connection might involve the Tanabata Star Festival; the conversation then turned to the Tanabata Yukata Festival. That speculation concerned the next bridge, not Nishigashibashi, and did not solve the June entry.

The order of the detectives’ route gives the list a practical presence in the investigation. Rather than remaining only handwriting on a calendar or paper, the names guide the detectives from one location to the next. Yet arriving at Nishigashibashi produces no corresponding discovery: the bridge can be located and its position in the sequence confirmed, while the reason it was paired with June remains unknown.

Reappearance and Investigative Significance

Kyoichiro Kaga later showed the twelve-bridge list to Hiromi Kadokura and identified the bridges as lying within his precinct. Hiromi recognized that Sakagami had previously shown her the same list while asking about it, and understood from Kaga’s explanation that he was investigating an angle connected to Oshitani’s murder. Nishigashibashi therefore belongs to a clue that moves between police inquiry, Koshikawa’s calendar, Kaga’s family history, and Hiromi’s awareness of the case. The list links people and objects without making their connection immediately legible.

That larger connection becomes more consequential when the investigation turns to Watabe. The detectives had been seeking a missing person known to both Hiromi Asai and Oshitani, and had focused heavily on Seizo Naemura until Yasuyo Miyamoto’s testimony indicated that Naemura was not the person they sought. Kaga then reasoned that Watabe had been connected to Hiromi for at least ten years, had few other known connections, and might have received financial support from her. Given Watabe’s estimated age, disappearance, and acquaintance with Oshitani, Kaga concluded that he could be Hiromi’s father, Tadao Asai. Investigators also found anomalies in the reported account of Tadao’s death: it appeared in the records of Biwa Gakuen Orphanage but lacked official documentation, and Hiromi’s former classmates did not recall her father’s suicide. Kaga inferred that Tadao might have used another person’s death to disappear and assume a new identity. Nishigashibashi is not itself the solution to that identity, but its place in the repeated list helps establish the documentary trail through which the investigation connects apparently separate lives.

Meaning and Limits of the Clue

The bridge’s narrative function rests on an important distinction: the list’s repeated structure is evidence of a connection, not proof of what that connection means. The June annotation matches across the calendar and the note, and Nishigashibashi is physically visited as part of the detectives’ effort to test the sequence against actual places. Still, no event or explanation is established for the bridge in the supplied evidence. Its unresolved status preserves the larger clue’s tension: a precise month and location can be recovered, while the human relationship behind the notation must be inferred from other evidence.