Edobashi Bridge is both a named point in a twelve-bridge sequence and a landmark on the detectives’ route through central Tokyo. The bridge’s importance is less a matter of a reported incident there than of its place among clues: the same name appears in a calendar and a separate list, linking an object recovered during the investigation to a question that Kyoichiro Kaga has struggled to answer.

The bridge in the twelve-name sequence

The calendar’s annotations assign one bridge to each month. Edobashi Bridge is the August entry, following Nihonbashi Bridge in July and preceding Yoroibashi Bridge in September. The other entries likewise name bridges in the Nihonbashi area, making the calendar read like an ordered itinerary rather than a collection of unrelated notes. Investigators learn that the annotations recur on every page, but their meaning remains unexplained at first.

A separate sheet found among the effects in Kaga’s mother’s apartment contains the same twelve names in the same monthly order. The exact correspondence with Mutsuo Koshikawa’s calendar makes the list a significant connection between the two pieces of evidence. Kaga explains that the note’s handwriting is not his mother’s and suggests that Shunichi Watabe may have written it. The identity of the writer and the purpose of the sequence therefore become questions for the investigation, rather than facts the list resolves on its own.

On the detectives’ river route

Edobashi Bridge appears again during a boat journey with Matsumiya and Fujisawa. After passing beneath Nihonbashi Bridge, the boat continues under Edobashi, Yoroibashi, Kayababashi, Minatobashi, and Toyomibashi before reaching the Sumida River. Rather than continuing along the customary tourist route toward Tokyo Skytree, Fujisawa turns back into the Kanda River. The journey gives the bridge a concrete place in the landscape that the calendar’s names had first presented as a puzzle.

The repeated passage from written sequence to travelled route underscores a distinction in the investigation: identifying the bridges is not the same as understanding why someone recorded them. Even after the route makes the names geographically legible, the calendar’s annotations remain an unanswered question. Edobashi Bridge thus functions as one link in a network of clues whose significance depends on their correspondence and on the relationships among the people connected to them.