“It’s your willingness to explore blind alleys, that’s what decides the outcome of a case”

Kyoichiro Kaga’s maxim that a case’s outcome depends on a detective’s willingness to explore blind alleys gives persistence a precise investigative meaning: it is the willingness to test uncertain paths, not a promise that every path will succeed. The saying comes from Kaga’s late father and is recalled after an investigation in Sendai has produced a useful lead, linking the family inheritance of the phrase to the detectives’ work of assembling proof.

Origin and Meaning

As Kaga and Shuhei Matsumiya look for a taxi on the main street, Matsumiya recalls the saying and asks whether it describes what they have just been doing. Kaga turns and grins in agreement. The phrase is not presented as a detached slogan: it names a practice the cousins have enacted by following leads whose value was not assured in advance.

Kaga’s late father had often used the maxim. Its survival in Kaga’s speech gives the investigative principle a personal inheritance, while Matsumiya’s recognition shows that the phrase can also serve as a shared account of their work. The wording makes outcome depend on willingness to enter dead ends, not on certainty that a lead will pay off.

The Method in Practice

The investigation illustrates why such persistence matters. In Mutsuo Koshikawa’s apartment, police found no ordinary personal identifiers; to seek DNA, they collected a toothbrush, a safety razor, and an old towel. The objects offered a practical route toward identifying Koshikawa, but Kaga immediately notes a weakness in the inference: a perpetrator could have switched them. The samples were useful evidence, not self-authenticating proof, and the possibility of substitution forced the investigators to keep uncertainty in view.

Another line of inquiry joined witness impression to forensic confirmation. Yasuyo Miyamoto recognized a sketch as resembling the Shunichi Watabe she had known, describing distinctive facial features as well as an impression of a man who kept his emotions bottled up. The detectives learned that Koshikawa had previously used Watabe’s name. The sketch’s value lay partly in conveying qualities a mechanically detailed facial composite might fail to evoke, but recognition alone did not settle identity.

A train timetable supplied a more objective connection. Forensic examiners found several prints on it matching prints from Koshikawa’s apartment; their number and location suggested that Watabe, rather than Kaga’s mother, had used the timetable most. That comparison supported the conclusion that Koshikawa and the man known in Sendai as Watabe were the same person. The investigative sequence moves from possible traces, through a witness’s response, to corroboration by fingerprints: persistence opens routes, while comparison gives the routes evidentiary weight.

Narrative and Thematic Role

The maxim frames detective work as a disciplined tolerance for uncertainty. The apartment’s stripped identity, the risk that personal items were switched, and the distinction between a persuasive likeness and physical trace each resist an easy conclusion. An apparent blind alley may still clarify what is unknown, expose a weakness in an assumption, or lead to evidence that can be independently checked.

Its force also comes from the balance between inherited wisdom and present procedure. Kaga’s father supplied the saying; Kaga and Matsumiya give it contemporary meaning through an inquiry that depends on both interpretive judgment and material corroboration. The phrase does not claim that every speculative lead is sound. It argues that a detective cannot know which avenues matter without being willing to investigate them—and must still distinguish a promising impression from proof.