Otsuki

Otsuki is a detective on the task force investigating Mutsuo Koshikawa and the man known in Sendai as Shunichi Watabe. His work follows the case into the nuclear power industry, where subcontracting and incomplete records obscure workers’ identities. By reporting a contact from Hamaoka Nuclear Power Station and later bringing forward Kazutoshi Yokoyama’s registration, he helps turn that institutional tangle into a concrete line of inquiry.

Identity and Investigative Context

Otsuki appears as one of the detectives working alongside Shuhei Matsumiya, Kyoichiro Kaga, Kobayashi, and the wider task force. The investigation is trying to establish who Koshikawa and Watabe were and how their identities connect to the case. Otsuki’s particular contribution is to pursue the nuclear-industry angle, a difficult avenue because workers were often hired through multiple layers of contractors and because the events under investigation dated back many years.

The industry’s recordkeeping offered no simple answer. Companies were required to retain employee documents for only three years for full-time workers, while short-term workers fell outside that requirement. Small firms and subcontractors could employ people under false names, and after the 2011 earthquake and tsunami, many smaller companies had left the business. The task force therefore sought information from power companies, contractors, former supervisors, and workers, with police across Japan assisting. Otsuki’s inquiries belong to this broad effort to recover a person’s history from a fragmented employment system.

Pursuing the Nuclear-Plant Lead

When someone from Hamaoka Nuclear Power Station contacted the task force, Otsuki set out to check the lead rather than assume it was reliable. Investigators hoped the contact might be a witness who recognized a man in a sketch. The task force had found no registration for either Watabe or Koshikawa among workers in radiation-controlled areas, though investigators considered that someone might have worked under either name outside those areas. An industry expert judged that unlikely: radiation exposure was where workers could earn the most, despite the share of their wages absorbed by middlemen.

The inquiries also pursued possible employment at Onagawa Nuclear Power Station. As the task force searched companies that might have employed Watabe or Koshikawa, it encountered a sprawling chain of satellite firms, many of which had since withdrawn from the industry. Otsuki’s Hamaoka contact thus represented a possible witness amid a much larger attempt to trace employment across companies whose records and personnel had dispersed.

Kazutoshi Yokoyama and the Registration Record

Otsuki later brought forward a name found in the registration center’s records: Kazutoshi Yokoyama. Yokoyama’s recorded address and legal domicile had both been in Nagoya, but his residence certification had subsequently been deleted without a recorded move, leaving investigators unable to establish where he lived. The missing current address made the registration a lead rather than a ready-made explanation.

The lead gained weight when Otsuki confirmed that Yokoyama had worked at Onagawa and had spent more than half of his career there. That employment history placed him at the very plant investigators were examining in their search for Watabe’s past. The discovery did not by itself settle the identity question, but it gave the task force a specific worker and career to investigate against the case’s uncertain names and scattered records.

Narrative Role

Otsuki’s role is procedural but consequential: he helps the investigation move from a general theory about itinerant nuclear-plant labor to a verifiable registration and employment history. His cautious response to the Hamaoka contact and his later report about Yokoyama mark two stages in that process—first testing whether a lead exists, then identifying a worker whose lengthy service at Onagawa makes the lead materially relevant. Through his work, the novel’s mystery of personal identity is set against an industry in which short-term hiring, subcontracting, and incomplete records make names difficult to verify.