Hashimoto Kankon

The bridge-name memo is a handwritten, month-by-month list whose matching appearance in a missing tenant’s calendar draws Kyoichiro Kaga’s family history into the investigation. At first, its twelve Tokyo bridges form an unexplained pattern; comparison with the calendar in Mutsuo Koshikawa’s apartment makes the paper evidence of a connection between Kaga’s late mother and the man known as Shunichi Watabe.

Description and Discovery

The memo lists one bridge for each month: Yanagibashi Bridge in January, Asakusabashi Bridge in February, Saemonbashi Bridge in March, Tokiwabashi Bridge in April, Ichikokubashi Bridge in May, Nishigashibashi Bridge in June, Nihonbashi Bridge in July, Edobashi Bridge in August, Yoroibashi Bridge in September, Kayababashi Bridge in October, Minatobashi Bridge in November, and Toyomibashi Bridge in December. Its orderly calendar structure is specific enough to be checked against another record, but the list alone does not explain why these bridges were associated with the months.

Kaga found the paper among his mother’s belongings and later showed a copy to Yasuyo Miyamoto. He explained that investigators had found the same bridge names handwritten on a calendar in the apartment in Kosuge. Miyamoto could not make sense of the memo, and Kaga put it back in his pocket, acknowledging that he himself could not interpret an item from his mother’s effects. The encounter emphasizes that possession of a family document did not mean Kaga knew its history.

The Calendar and the Handwriting Link

The bridge list became an investigative clue because it matched the calendar annotations in Koshikawa’s apartment. The task force commissioned two detailed handwriting analyses: one of those annotations and one of the note Kaga had provided. The experts concluded that both were written by the same person. The match established a material link between a document preserved among Kaga’s mother’s belongings and a calendar kept in the apartment of a man whose identity and whereabouts were uncertain.

Kaga was careful about what the comparison did and did not establish. The note had been found in his mother’s apartment, but he said he did not know whether it had belonged to her; its handwriting was clearly not hers. He suspected that Watabe had written it, yet admitted he knew almost nothing about the man and had never worked out the list’s meaning. The memo therefore supplied a connection, not an immediate explanation or a confirmed authorship.

Kaga’s Family History and the Memo’s Limits

When investigators discussed the handwriting results, Kaga told his superiors that his mother had maintained a long-term relationship with Watabe. He proposed that Watabe was the likely author of the list, but framed this as a guess rather than a fact. Because the paper was among his mother’s effects, it brought the concealed relationship into the investigation while leaving unresolved who had written it and why the bridges had been arranged by month.

The memo also shows the limits of what the people around Kaga could contribute. Miyamoto, asked directly whether the copy meant anything to her, said she did not know. Kaga’s willingness to hand over all of his mother’s effects as evidence reflects how the investigation had crossed into his own unresolved family past: potentially relevant objects were available, but their significance had to be established through comparison and further inquiry rather than personal recollection.

Identification and Narrative Significance

Later, the investigation established through fingerprint comparison that the man known in Sendai as Shunichi Watabe and Mutsuo Koshikawa, the tenant connected to the calendar, were the same person. That finding gave the memo’s handwriting match greater significance: the document found among Kaga’s mother’s belongings and the calendar in Koshikawa’s apartment were not merely similar records associated with unrelated men. The evidence tied both to the same individual, though it did not by itself prove the memo’s authorship.

Kaga’s broader reconstruction went further. He reasoned that Watabe’s long connection with Hiromi Asai, his limited dealings with others, his estimated age, and his acquaintance with Michiko Oshitani pointed toward Watabe being Hiromi’s father, Tadao Asai. The memo is one link in that chain rather than its conclusion: handwriting connects the documents, fingerprints connect Watabe with Koshikawa, and the investigation’s other evidence supports the proposed identity. Its understated list of bridges becomes a portable trace of relationships that had remained hidden, linking a private archive to the police inquiry without explaining itself on its own.