Annotated puppy calendar

The Annotated puppy calendar is the unlikely key to a chain of discoveries about Mutsuo Koshikawa’s concealed identity. A cheerful, mass-produced calendar stood out in his chillingly sterile apartment; its handwritten names of bridges in Nihonbashi seemed at first to point toward events or places that investigators could not verify. Yet the annotations gave Kyoichiro Kaga a pattern to pursue, linking Koshikawa’s otherwise erased domestic life to evidence that would eventually identify him as Shunichi Watabe and reopen the question of Hiromi Asai’s past.

Appearance and discovery

The calendar’s puppy photographs made it an especially strange presence in an apartment without decoration. It hung beside the window, while the room’s sterile emptiness offered almost nothing to explain its tenant: investigators found no personal photographs, identity documents, letters, or other ordinary traces of who Koshikawa was. The contrast made the calendar memorable, but not immediately informative. A search-team member had remarked that the same calendars were sold in pet shops nationwide, and no neighbor recalled Koshikawa owning a pet; investigators therefore had no reason to think the object was a personal memento.

During a later review of items recovered from the apartment, Kobayashi pulled the calendar from a box and noticed writing in the bottom-right corner of the April page: “Tokiwabashi Bridge.” The discovery turned an unremarkable commercial object into a puzzle. The search team had already seen similar marks on other pages, but the scattered names had not yet yielded a usable lead. Matsumiya knew the annotations were present throughout the calendar, although their purpose remained obscure.

The twelve bridge annotations

The markings form a month-by-month sequence rather than a single note: January names Yanagibashi Bridge; February, Asakusabashi Bridge; March, Saemonbashi Bridge; April, Tokiwabashi Bridge; May, Ichikokubashi Bridge; June, Nishigashibashi Bridge; July, Nihonbashi Bridge; August, Edobashi Bridge; September, Yoroibashi Bridge; October, Kayababashi Bridge; November, Minatobashi Bridge; and December, Toyomibashi Bridge. The list’s regularity suggests an arrangement, but the calendar itself does not explain what the arrangement records.

Investigators recognized that the named bridges were in the Nihonbashi area. The search team considered whether Koshikawa might have attended events held on them, but its inquiries uncovered no such events, and the unexplained annotations delayed the team’s report. In this way the calendar offered both a specific geographical pattern and a conspicuous absence of confirmation: it pointed toward Nihonbashi without yet saying why.

From clue to investigative lead

The annotations reached Kaga through Matsumiya. While speaking with his cousin, Matsumiya mentioned that a calendar in Koshikawa’s apartment bore names including Tokiwabashi Bridge and Nihonbashi Bridge. Kaga reacted with immediate physical urgency, gripping Matsumiya’s shoulder and pulling him back before demanding more detail. Once Matsumiya had returned to his seat and recounted what he knew, Kaga began testing his memory of the sequence, asking which bridge appeared in February and checking the order of the entries.

That exchange marks the calendar’s shift from a baffling item in an evidence box to an active investigative lead. The names’ exact order mattered to Kaga, even though Matsumiya initially struggled to recall it. The scene does not itself disclose the interpretation Kaga will reach, but it establishes that the calendar’s pattern connects with knowledge or evidence he considers important; what had seemed to the search team like an opaque list is now driving the investigation forward.

Identity and the larger pattern

The calendar belongs to a case built around identities that have been deliberately obscured. Koshikawa had lived in his apartment for nine years without updating his residence certificate, and the Maebashi address on his original Tokyo paperwork proved unproductive and was suspected to be false. With the apartment stripped of personal effects, investigators had to assemble a history from scattered material evidence. The bridge names were one such fragment: unlike an identity card or letter, they did not identify their writer, but they preserved a repeated pattern associated with the otherwise untraceable tenant.

Other forensic discoveries eventually confirmed that Koshikawa and the man living in Sendai under the name Shunichi Watabe were the same person. The calendar’s role is distinct from that fingerprint evidence: it supplies a geographical and patterned clue, while the prints establish identity through comparison. Together, such fragments let the investigation move beyond the false names and missing records that had kept Koshikawa’s life inaccessible.

The investigation also reaches back to Tadao Asai, whose reported death had no support in official records beyond an orphanage file. Kaga’s reconstruction was that Tadao had used another man’s death to disappear, leaving his daughter Hiromi to confirm the false identity. The calendar does not establish this history by itself, nor does its list directly explain the deception. Its significance lies in the way it joins a seemingly trivial object to a wider inquiry in which a residence record, fingerprints, a newspaper account, and family testimony must each be read against the possibility of substituted identities. What the apartment had preserved was not an open confession but a repeated, unexplained trace—twelve bridge names waiting to become legible in context.