On February 28, 1989, a 23-year-old elementary school teacher named Yumi Tanaka returned to her dormitory in Miyakoji village after visiting family. What she found in the bathroom would become one of Japan’s most perplexing unsolved deaths.
Naoyuki Kanno, a 26-year-old nuclear power maintenance worker, was discovered dead inside the septic tank beneath the toilet. The circumstances of his death have defied explanation for more than three decades.
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The Discovery
Tanaka initially noticed a black shoe inside the toilet opening. Confused and frightened, she stepped outside to check the outdoor access point of the U-shaped concrete septic system. Two bare human feet were visible through the tank opening.
Police and firefighters arrived but faced an immediate problem. The external pipe opening measured only 36 centimeters wide. The septic tank itself stood 107 centimeters high. Kanno’s body measured approximately 120 centimeters tall.
Crews had to cut open the concrete structure to retrieve the body. What they found inside made no physical sense.
The Physical Impossibility
Kanno’s body was wedged horizontally in the cramped space. He was naked from the waist up, with his coat folded across his chest. One black shoe lay near his head. His car was found nearby, unlocked with keys still in the ignition.
The autopsy revealed death by hypothermia on February 26, two days before discovery. Aside from minor scratches on his elbows and knees, there were no injuries. No signs of struggle. No trauma consistent with forcing a human body into such a confined space.
Kanno’s father later used the cut sections of the septic tank to attempt recreating the scenario. He concluded it was physically impossible for anyone to enter the space voluntarily, clothed or unclothed.
Key Timeline:
- February 23: Kanno attended a Youth Association farewell party
- February 24: Last seen by his father; reported missing (national holiday for Emperor Hirohito’s funeral)
- February 24-27: Teacher Tanaka away from dormitory
- February 26: Estimated time of death
- February 28: Body discovered
Who Was Naoyuki Kanno?
Kanno worked as a sales manager for a company providing maintenance services to Fukushima’s nuclear power facilities. He served as president of the local Youth Association and was known throughout the village as reliable and sociable. He worked as an MC at weddings and helped with community events.
Nothing in his background suggested the behavior police would later attribute to him.
The Official Conclusion
Fukushima police ruled the death accidental. Their theory: Kanno entered the septic tank to spy on the female teacher and became trapped, dying from hypothermia.
The village exploded in protest. More than 4,000 residents signed a petition demanding reinvestigation. They knew Kanno. The official explanation didn’t fit.
Problems with the official theory:
- Teacher Tanaka was away visiting family from February 24-27
- Kanno knew about her absence
- No evidence of prior voyeuristic behavior
- Physical impossibility of entering the space
- Minimal injuries inconsistent with struggling in confined space
- Car left unlocked with keys inside (suggesting quick stop, not planned activity)
The Nuclear Connection
Two months before his death, an incident occurred at Fukushima Daini Nuclear Power Plant Unit 3. From late December 1988 through January 4, 1989, the reactor alarmed multiple times. According to later reports, TEPCO executives ordered workers to ignore alarms and control pressure manually because inspections were scheduled for January 6.
On January 4, 1989, the section head responsible for maintenance jumped in front of a train at Ueno Station in Tokyo. It was ruled suicide.
Government officials questioned Kanno about the nuclear incident. Some in the village believed Kanno was investigating his colleague’s death and suspected it wasn’t suicide.
Suspicious Circumstances
After Kanno’s death, several unusual events occurred:
Every officer from Miharu Police Station was transferred to other locations. The coroner who examined Kanno’s body quit after 34 years on the job. The body was thoroughly cleaned twice before any detailed autopsy could be performed.
Yumi Tanaka, the teacher who found the body, was engaged to the son of Tadashiro Watanabe’s election campaign strategist. Watanabe served as village headman for over 30 years. According to some sources, Kanno had supported Watanabe’s campaign but withdrew after discovering corruption.
After the incident, Tanaka received an award and a model house from TEPCO.
The Documentary Evidence
In 1996, filmmaker Fumiki Watanabe produced a documentary titled “Fukushima Mystery.” Using hidden cameras and recorders, he interviewed villagers about the case. The film captured the village headman’s uncomfortable responses when questioned about Kanno’s death.
Watanabe identified Tanaka as the most problematic witness. Despite numerous attempts, she never spoke publicly about what happened. The teacher had reportedly been receiving strange phone calls before Kanno’s death. The calls stopped after his body was discovered.
Case Closed, Questions Remain
In 2004, when the statute of limitations expired, police officially closed the case as an accidental death. No fresh investigation was ever opened despite the petition signed by nearly half the village.
The Naoyuki Kanno case remains one of Japan’s most disturbing mysteries. The strange death of this young maintenance worker continues to generate discussion online, with the case experiencing renewed attention on social media platforms and true crime podcasts in recent years.
Unresolved Questions:
- How did Kanno’s body end up in a space physically too small for entry?
- Why were there no significant injuries?
- What was his relationship to the teacher?
- Was his death connected to the nuclear plant incident?
- Why were all investigating officers transferred?
Miyakoji village itself became part of the Fukushima evacuation zone after the 2011 nuclear disaster. Most residents have since returned, but the memory of what happened in 1989 lingers.
The truth about what happened to Naoyuki Kanno on that February day may never be known. What remains is a case that challenges physical logic, a community convinced justice was never served, and a family still seeking answers about how their son died in such inexplicable circumstances.
