The great outdoors has always been a place of refuge and escape, especially after difficult times. For many, hiking in nature provides a perfect opportunity to disconnect from the stresses of everyday life. Yet, the wilderness holds mysteries that can turn a simple trek into something far more sinister.

In 1989, a peculiar rescue operation in Japan's Daisetsuzan National Park unveiled one of hiking's most perplexing mysteries. What began as a search for two missing hikers led to the discovery of a massive SOS sign made from birch trees, visible from the air. Though the original hikers were found safe, they had never created this distress signal - opening the door to a five-year-old disappearance case that would challenge investigators with conflicting evidence, mysterious recordings, and remains that told an incomplete story.

Key Takeaways

An unexplained SOS sign made of cut birch trees led rescuers to discover human remains and personal belongings from a missing hiker.
A disturbing cassette recording found with the remains featured a voice different from the identified victim, creating an unsolved mystery element.
Despite initial confusion about the identity of the remains, authorities eventually attributed them to a man who had disappeared five years earlier on the mountain.

The Lure of Nature and Initial Insights

The call of the wilderness often provides an escape from the demands of daily life, yet nature's beauty can conceal unexpected dangers. In July 1989, a puzzling discovery unfolded in Japan's Daisetsuzan National Park when two missing hikers became entangled in a much deeper mystery.

During a rescue operation for these hikers, helicopter crews spotted an enormous SOS signal constructed from precisely cut birch trees. The signal measured an impressive 18 meters long and 5 meters tall, visible from the air despite being located in a remote area approximately four kilometers south of Mount Asaidake's summit.

Police immediately investigated the distress signal, believing it connected to the missing hikers. In a strange twist, they located the hikers about a kilometer north of the sign. When informed about the SOS that had facilitated their rescue, the hikers expressed complete confusion - they had created no such signal.

This puzzling coincidence prompted a second search the following day, yielding disturbing discoveries. Most notably, investigators found human remains 10-30 meters from the SOS sign. The bones showed evidence of animal gnawing and several fractures suggesting the person had suffered serious injuries before death.

About 165 feet north of the sign, searchers discovered additional items buried beneath tree roots:

A backpack
A Sony tape recorder
Three cassette tapes
Basic toiletries and supplies
An ID card belonging to Kenji Iwamora, a hiker missing for five years

Initial analysis from Ashikawa Medical University classified the remains as belonging to a woman with type O blood. This assessment created further confusion since the discovered items appeared masculine in nature.

The cassette tapes contained mostly anime soundtracks, but one held a chilling recording. A male voice pleaded in Japanese: "I can't move. I'm on the cliff. SOS help me. The place is where I met the first helicopter. I can't go up. Deeply sasa. Lift me up from here."

This recording presented additional questions. The voice mentioned being stranded on a cliff, yet the items were found in a valley. The reference to "sasa" (dense bamboo) added another layer of confusion to the already perplexing scenario.

Information about Iwamora proved difficult to obtain. Japanese media typically redacted his name, with only the Associated Press providing limited details. He was described as an office worker who failed to return to work, prompting concern about his whereabouts.

When contacted by reporters, Iwamora's family confirmed the backpack belonged to their son but expressed uncertainty about whether the voice on the recording was his. This raised the possibility that multiple individuals were involved in this mysterious incident.

Further investigation revealed the SOS sign had existed long before its 1989 discovery. Aerial photographs taken by the forestry agency in September 1987 showed the sign was already visible, though barely discernible at that altitude.

After reassessing the remains, Ashikawa Medical University revised their conclusion, stating they had made an error in their initial analysis. The bones actually belonged to a male with type A blood, allowing investigators to conclude they were Iwamora's remains. With no obvious signs of foul play, authorities closed the case.

The Mountain Mystery Unfolds

Discovery of the Distress Signal

On July 24, 1989, a search and rescue operation was underway in Daisetsuzan National Park, Japan. Two hikers had gone missing in the area surrounding Mount Asaidake, prompting helicopter searches throughout the day. As daylight waned, rescue crew members spotted something unusual on the ground below them. An enormous SOS signal, measuring 18 meters long and 5 meters tall, had been created using precisely cut birch trees. This distress signal was located approximately four kilometers south of Mount Asaidake's summit, in an area without trails that rarely saw human visitors.

The local police immediately landed to investigate the area surrounding the massive signal. Their search efforts proved successful when, about a kilometer north of the sign, they located and rescued the two missing hikers. The rescue team informed the hikers that finding them would have been significantly more difficult without the SOS sign guiding them to the general area.

Hikers' Puzzling Rescue

The rescued hikers responded with confusion when told about the SOS sign. They stated they had never created any such signal and had no knowledge of its existence. This revelation transformed what seemed like a successful rescue into a much deeper mystery. If the hikers hadn't created the sign, who had?

The following day, police organized a second search of the area, yielding disturbing discoveries. Most notably, they found human remains—a skeleton with gnaw marks consistent with wild animal activity and broken bones suggesting severe injury—located 10-30 meters from the SOS sign. Additionally, about 165 feet north of the sign, searchers discovered a backpack buried in a hole beneath tree roots, just large enough to fit a single person.

Backpack contents:

Sony tape recorder
Three cassette tapes (two anime soundtracks, one with a recorded message)
Basic toiletries
Various hiking supplies
ID card belonging to Kenji Iwamura, a hiker missing for five years

The recorded message contained a male voice desperately calling for help: "I can't move. I'm on the cliff. SOS help me. The place is where I met the first helicopter. I can't go up deeply. Sasa lift me up from here."

Initial forensic analysis from Ashikawa Medical University identified the remains as belonging to a woman with type O blood. This assessment complicated matters, as the belongings didn't seem to match with a female victim. After further examination, the medical university revised their findings, declaring the remains belonged to a male with type A blood—consistent with Iwamura.

Aerial photographs later revealed the SOS sign had been visible from at least September 20, 1987, appearing in forestry mapping images taken from 3,700 meters above. With no evidence of foul play and the identification of the remains as likely belonging to Iwamura, authorities eventually closed the case.

Deepening the Investigation

Human Remains and Field Discoveries

The search operation took an unexpected turn when investigators conducted a thorough examination of the area surrounding the SOS sign. Approximately 10-30 meters from the carefully arranged birch trees, they discovered a collection of human skeletal remains. The bones showed evidence of animal activity, with visible gnaw marks suggesting wildlife had disturbed the remains after death. Several bones displayed fractures, indicating the individual likely suffered significant injuries before death.

In a separate discovery about 165 feet north of the sign, search teams found a backpack concealed beneath tree roots in a hole just large enough to accommodate a single person. The backpack contained several items:

Three cassette tapes
A Sony tape recorder
Basic toiletries
Miscellaneous hiking supplies
An identification card

The ID card belonged to Kenji Iwamura, an office worker who had disappeared approximately five years earlier. Initial confusion arose when experts from Ashikawa Medical University classified the skeletal remains as belonging to a female with type O blood, which seemed inconsistent with the personal items found.

The Puzzling Audio Evidence

The cassette tapes recovered from the backpack added another layer of mystery to the investigation. Two tapes contained anime soundtracks, while the third held a disturbing recording. A male voice had recorded a desperate message:

"I can't move. I'm on the cliff. SOS help me. I can't move on the cliff. SOS help me. The place is where I met the first helicopter. I can't go up deeply sasa. Lift me up from here."

The recording mentioned being trapped on a cliff and referenced "sasa," a type of dense bamboo. This detail confused investigators since the remains and SOS sign were discovered in a valley rather than on a cliff face.

When authorities contacted Iwamura's family, they confirmed the backpack belonged to their missing son. However, they expressed uncertainty about the voice on the recording, unable to definitively identify it as Kenji's voice.

Further investigation revealed the SOS sign was visible in aerial photographs taken by the forestry agency on September 20, 1987, suggesting it had remained undetected for years. After reassessment, medical experts corrected their initial findings, concluding the remains actually belonged to a male with type A blood, which aligned with Iwamura's profile.

Looking at the Key Facts

The Backpack Owner's Identity

The mysterious case centers around a backpack found near an SOS sign in Daisetsuzan National Park, Japan. The backpack contained several personal items including three cassette tapes, a Sony tape recorder, toiletries, and other basic supplies. Most significantly, investigators discovered an ID card belonging to Kenji Iwamora, an office worker who had disappeared about five years earlier while hiking in the area.

Information about Iwamora is limited and contradictory. Some reports suggested he had recently developed an interest in outdoor activities, while others claimed he wasn't someone who would typically hike alone. There were also accounts that he may have been celebrating a work promotion with this mountain trip.

Interestingly, when authorities contacted Iwamora's family, they confirmed the backpack belonged to him but could not verify whether the voice on one of the cassette tapes was their son's.

Who Created the SOS Signal?

The SOS sign that sparked this investigation measured approximately 18 meters long and 5 meters tall, constructed from precisely cut birch trees. It was discovered approximately 4 kilometers south of Mount Asaidake's summit in an area without trails and rarely visited by hikers.

The sign's discovery is particularly puzzling because:

No cutting tools were found in the vicinity
The trees were precisely cut and arranged
The two hikers rescued near the area in July 1989 confirmed they hadn't created the sign

What makes this element of the case even stranger is that the SOS sign had been present for quite some time before being noticed. Aerial photography from the forestry agency and the Geospatial Information Authority of Japan revealed the sign was visible in a photograph taken on September 20, 1987 - approximately two years before the rescue operation that brought attention to it.

What the Aerial Evidence Revealed

The aerial photograph, taken from approximately 3,700 meters above ground, showed the SOS sign measuring about 0.9 millimeters wide in the image. While the first "S" appeared somewhat unclear, the "O" and final "S" were more distinct. This photographic evidence confirmed the sign existed at least as early as September 1987.

This timeline aligns with Iwamora's disappearance, placing the sign's creation within the appropriate timeframe. The photograph proved critical to understanding that the distress signal had been present but unnoticed for years.

The regular five-year schedule of aerial photography also helped investigators determine that the sign was created sometime after 1982, as it didn't appear in earlier images. This photographic evidence serves as one of the few concrete facts in an otherwise mysterious case.

Final Revelations and Unanswered Mysteries

Bone Analysis Correction

The investigation took an unexpected turn when the forensic experts at Ashikawa Medical University reassessed their initial findings. Their first report had identified the skeletal remains discovered near the SOS sign as belonging to a female with type O blood. This misidentification temporarily complicated the case, creating confusion about whose remains were actually found. Upon further examination, the experts reversed their conclusion, determining that the bones actually belonged to a male with type A blood. This critical correction allowed investigators to connect the remains to the missing hiker, Kenji Iwamora, whose backpack and identification had been found buried nearby. The bones showed evidence of gnaw marks from wild animals and several fractures, suggesting the individual had suffered significant injuries prior to death.

Case Resolution

After the corrected forensic analysis matched the remains to Iwamora, authorities considered the primary mystery solved. The timeline aligned with Iwamora's disappearance approximately five years earlier, and aerial photography from the Forestry Agency confirmed the SOS sign had been visible since at least September 1987. The meticulously arranged birch trees forming the 18-meter long distress signal had been created sometime between 1982 and 1987, consistent with when Iwamora went missing. Despite solving the identity question, several elements remained unexplained:

No cutting tools were found that could explain how the birch trees were precisely cut
The voice on the cassette tape recording wasn't definitively identified by Iwamora's family
The recording mentioned being trapped on a cliff, yet the remains were found in a valley

With no evidence of foul play discovered during the investigation, authorities ultimately closed the case, attributing the death to a hiking accident. The bizarre coincidence that the SOS sign helped rescue two completely unrelated hikers years later remains one of the most striking aspects of this mysterious mountain incident.

The Mysterious Daisetsuzan SOS Sign: Japan's Unsolved Hiking Disappearance