Fukushima Prefecture is both a place in Tadao Asai’s post-disappearance life and a point of contact between his carefully concealed identity and the investigation into Mutsuo Koshikawa. After a staged death enabled him to escape his former life, Tadao worked at nuclear power stations and sent letters from Fukushima under an assumed identity; years later, the same region belonged to the trail investigators followed through an industry where employment and records were difficult to trace.

A Place in Tadao Asai’s Hidden Life

Tadao’s connection to Fukushima began after he arranged for another man’s death to be taken for his own. His daughter, Hiromi Asai, was placed in an orphanage, while Tadao continued living under an assumed identity. A month after her arrival, his first letter reached her from an address somewhere in Fukushima Prefecture. The sender used the name Kyoko Kondo, in keeping with their agreement, and wrote as though a father and daughter had moved because of his work.

The letter offered Hiromi a narrow but vital assurance: Tadao was alive and working at a nuclear power plant. He described his main task as cleaning up radiation and told her he was managing. Hiromi understood that he was passing himself off as Kazutoshi Yokoyama, the man whose identity he had taken, a name she associated with painful circumstances. Their correspondence gave her proof of her father’s continued existence without making an in-person reunion possible.

Work, Movement, and Precarious Records

Fukushima appears within a wider pattern of itinerant nuclear-industry work. Tadao described himself as going from one plant to another, having just finished inspection and maintenance at the Mihama plant before heading to Fukushima. Another worker explained that such employment could mean a succession of temporary assignments, company dormitories, and subcontractors far down a chain of smaller firms. For Tadao, this mobile, insecure working world made a life without a stable home possible.

The structure of that industry also shaped the police inquiry. Investigators found that employee records were often retained only for a limited period, while short-term workers could be hired through layers of contractors and subcontractors. After the 2011 earthquake and tsunami, some smaller companies had left the business altogether. Police therefore contacted employers and former workers across the country, but tracing a worker who had used a false name was especially difficult. The account links Fukushima not just to Tadao’s location, but to the labor system that helped obscure who he was.

Letters and Separation

Tadao’s letters from Fukushima turned distance into a routine rather than a reunion. Hiromi replied immediately, and the two exchanged a letter each month. The letters let them maintain a father-daughter relationship while concealing their identities, but the arrangements they relied on also kept them apart: Tadao’s work offered little opportunity to travel, and any meeting risked recognition by someone who knew them.

Even when Tadao later worked at the Ohi Nuclear Power Station, which was not far from the orphanage, they still did not meet. His correspondence could convey that he was continuing his life, but it could not restore ordinary family life. Fukushima thus marks a fragile form of contact—sustained through an alias, a company address, and regular letters, yet bounded by the secrecy that had made their separation possible.

Investigative Significance

The investigators’ account of Mutsuo Koshikawa shows how easily a person could become difficult to locate. His apartment contained no identifying personal items, and the residence information he had supplied when moving to Tokyo appeared false. Later, matching fingerprints on a timetable established that Koshikawa and the man known in Sendai as Shunichi Watabe were the same person. That connection brought the investigation into the orbit of nuclear-plant work, where a false name and employment through contractors could leave little straightforward documentary trail.

Fukushima’s significance is therefore not that the evidence identifies it as the sole location of Tadao’s concealed life or the investigation’s decisive discovery. Rather, it is one concrete destination within a mobile working life, and the place from which his concealed family relationship was briefly maintained by post. Against the apparent solidity of official identities, addresses, and employment records, the letters and the scattered work history reveal how a life could persist while remaining difficult to document.