The Arakawa River serves as a point of geographic comparison in the investigation of two separate killings. Its banks locate the Shinkoiwa murder, while a second crime scene near the river gives Shuhei Matsumiya a reason to ask whether the cases might be connected. The river’s significance is therefore investigative rather than scenic: distance becomes a clue to test, not proof of a shared crime.

The Shinkoiwa Crime Scene

Late on the night of March 12, a makeshift tarpaulin structure by the river caught fire. A man’s body was found inside. The death was initially treated as an accident, but an official autopsy found that the victim had not inhaled smoke and had marks indicating strangulation. Those findings changed the case from an apparent fire death into a murder investigation.

The victim was believed to be a homeless man known in the neighborhood, but police had not established his identity. A DNA comparison was conducted to test for a connection with the case involving Michiko Oshitani; it showed that the burned body was not that of the missing Mutsuo Koshikawa. The riverbank thus became the setting of a distinct case, while the attempt to identify the victim also brought it into the orbit of another investigation.

Geographic Link to the Oshitani Case

Shuhei Matsumiya points out that the Oshitani murder took place near the Arakawa River, whereas the Shinkoiwa crime scene lay directly on its banks. He estimates that the two locations were roughly five kilometers apart. For him, the closeness of both the dates and the sites makes the relationship worth examining.

Kobayashi urges caution. The Shinkoiwa victim had apparently died by suffocation, possibly through manual rather than ligature strangulation, and Kobayashi considers it rash to infer a connection from the dates alone. Ishigaki likewise says that the distance is open to interpretation and that the police cannot interfere in another precinct’s case on the basis of Matsumiya’s intuition. That precinct already has its own task force. He agrees only to note the concern, then directs Matsumiya to continue investigative work in Shiga.

Investigative Significance

The river does not establish that the two crimes share a perpetrator or motive. Instead, it supplies a concrete spatial comparison that Matsumiya puts before his superiors and they decline to treat as conclusive. The contrast between the two locations—one near the river, the other on its bank—captures the difference between noticing a possible pattern and proving one.