Three stories about the mountains.
First story:
An acquaintance of my parents was an avid climber, and this is a story he told. He was a hardcore enthusiast whose hobby was "route finding"—making his way through areas without established trails. According to him, when you go deep into the mountains, you can see things scaling sheer cliffs at incredible speeds. Naturally, whatever they are, they are definitely not human.
Second story:
When I was in college, I joined the wandering and mountaineering club. An upperclassman in the club told me about a night when they were in the snowy mountains, pitching their tents inside a refuge hut. In the dead of night, despite the fierce blizzard raging outside, they heard the distinct clanking sound of someone taking off crampons—the iron spikes attached to mountaineering boots for snow. Yet, no one ever came inside. There is no way anyone would be handling crampons out in a midnight blizzard, and even if they were, it makes no sense that they wouldn't enter. The senior told me that the spirits of lost climbers wander about in this exact manner.
Third story:
After starting work, I had some free time and spent a short while in an adult mountaineering club. I quit climbing after that because I had a terrifying near-miss with a disaster. It happened when our three-person party went ski-mountaineering in the Azuma mountain range in Fukushima. We went in trusting a forecast that said the weather would clear up, but the weather never improved and the blizzard just kept going. We should have turned back, but having gone in too deep, our party of three was caught in a complete whiteout, lost our way, and before we knew it, dusk was falling and night had arrived. To avoid freezing to death, we had to push through the forest without sleep, wandering around until very late at night. As a side note, when humans reach extreme conditions, you start seeing hallucinations. In my case, I remember being heavily messed with because I kept seeing a "house" through the trees. I'd think, "Oh, there's a house," and approach it, only to find nothing but more woods… That is a pretty unpleasant experience. The member walking in front of me was getting angry, and the member in the back started talking in an increasingly incoherent way as time went on. Honestly, it's a completely miserable memory.
After that, we found the Keio Hut and our lives were saved, but the next day, which dawned clear and sunny, the Self-Defense Forces were dispatched for search and rescue operations. Because of the previous day's forecast, it seemed quite a few other people besides us had been trapped in the snowy mountains. According to the old man who ran the Keio Hut, among the people heading toward the hut, there were some who "never arrived." I don't know if it belonged to one of them, but we heard a report that right in the middle of the trail leading to the hut, a single ski was found stuck vertically into the snow. In the dead of night, when skis are your only means of transportation, there is no way anyone would stick one into the snow like that. Especially just one… You would never let go of skis that your life depends on. Just based on intuition, I think the owner of that ski probably saw something right at the end, or lost their mind. In a place like that, it wouldn't be strange at all for something like that to happen.