Calendar with the twelve bridge names

The Calendar with the twelve bridge names is a puppy-picture flip calendar found in the Kosuge apartment, its pages marked with a different bridge for each month. Its importance lies in the contrast between its ordinary appearance and the attention its owner gave it: Mutsuo Koshikawa had filled in the bridge names for the whole year, and Kyoichiro Kaga reasons that each changing page could prompt Koshikawa to visit that month’s bridge. The calendar thus turns a domestic object into a possible record of repeated intention—and a link between the investigation and Kaga’s family history.

Description and Discovery

The calendar was found in the Kosuge apartment. It was a flip calendar with one month on each page and pictures of puppies. The handwritten bridge names were its distinctive feature: one bridge was assigned to every month, transforming a familiar household calendar into a year-long sequence of locations.

The calendar’s pattern echoed a separate sheet of paper found in Kaga’s mother’s apartment. That note listed a bridge for each month, and the dates and places matched those written on Koshikawa’s calendar. The handwriting on the note was clearly not Kaga’s mother’s, and its ownership was uncertain. Kaga told his superiors that his mother had maintained a long-term relationship with Shunichi Watabe; he suspected Watabe may have written the list, but admitted he did not know what it meant. The calendar therefore entered the case as part of a larger, unresolved connection among Koshikawa, Watabe, and Kaga’s mother.

The Monthly Sequence

The calendar’s monthly entries were not merely a record of places already visited. Kaga focused on the fact that Koshikawa had written the bridge names for April and all the remaining months even though Koshikawa was murdered in March. That advance marking suggested to Kaga that Koshikawa had written the sequence onto the calendar as soon as he obtained it—and that the bridges mattered to him enough to plan for them throughout the year.

Kaga tested the idea against the calendar’s changing pages. In April, the named bridge was Tokiwabashi Bridge; when the month turned to May, the page would be flipped to reveal Ichikokubashi Bridge. He proposed that Koshikawa might read the new entry as a reminder to go to that bridge during that month. On a boat passing beneath Tokiwabashi Bridge, Kaga pointed out that the current month’s bridge could command attention to the exclusion of the others. The calendar’s arrangement thus offered a simple mechanism for turning a written list into a series of recurring prompts.

Investigative Significance

Kaga’s interpretation did not establish why Koshikawa visited the bridges, but it gave the calendar a possible function beyond keeping track of dates. Its monthly structure could explain how the names remained present in Koshikawa’s routine: each page change brought one location to the foreground. The puppy pictures and commonplace format conceal, rather than announce, the possible purpose of the annotations.

The investigation had already identified a connection between Watabe and Hiromi Asai, while testimony from Yasuyo Miyamoto had shown that Seizo Naemura was not the missing man the detectives sought. Kaga subsequently reasoned that Watabe’s long connection to Hiromi, his limited ties to others, his estimated age, his disappearance, and his acquaintance with Michiko Oshitani pointed toward Watabe being Hiromi’s father, Tadao Asai. That deduction gave the bridge list in Kaga’s mother’s apartment a possible place in the same network of relationships, but the calendar itself supplies no definitive explanation of the bridges or their significance.

Meaning and Limits

The calendar works as a quiet object of suspense: its visual ordinariness sits beside a pattern precise enough to invite explanation. Each month offers a new place, while the year-long advance of the entries suggests purpose that the detectives must reconstruct from incomplete traces. The object’s evidentiary force is therefore suggestive rather than conclusive. It helps Kaga frame a plausible account of Koshikawa’s repeated attention to the bridges, while the matching note and the unresolved identity of its writer keep the calendar connected to questions about Watabe and Kaga’s mother.