Experience the transformative power of forest bathing with Coconuts Hike Japan. Our guided walks in Hakone offer a serene escape from the hustle and bustle of everyday life, allowing you to reconnect with nature and yourself.

In physics, there is a phenomenon called 1/f fluctuation — pronounced “one-over-f fluctuation” and known in Japanese as yuragi (ゆらぎ), meaning a gentle wavering or oscillation. It describes a specific mathematical relationship in wave patterns: one that sits precisely between pure order and pure randomness.

Think of it this way. A metronome is perfectly regular — every beat identical, every interval the same. It is predictable, and after a while, it becomes numbing. White noise, on the other hand, is completely random — all frequencies at once, no pattern at all. It quickly becomes exhausting and unsettling.

1/f fluctuation is neither of these. It is the sweet spot between them: regular enough to feel safe and comprehensible, varied enough to remain alive and interesting. Researchers describe it as a “moderate blend of regularity and irregularity, predictability and surprise” — and the human nervous system, it appears, is deeply attuned to it.

When the body perceives 1/f fluctuation through the senses — through what we see, hear, feel, and smell in a forest — a cascade of responses may follow. According to the research of Japanese physicist Toshimitsu Musha, one of the key mechanisms is the stimulation of alpha waves (α-waves) in the brain.

You may have encountered alpha waves in the context of meditation or sleep. They are associated with a state of relaxed alertness — not drowsiness, not anxiety, but the calm, open awareness that most of us find very difficult to access during a normal working day. Alpha waves are the brain’s way of saying: I am safe, I am present, I can rest.

Alongside this, exposure to natural 1/f environments is thought to help regulate the autonomic nervous system — the part of our nervous body that governs heart rate, breathing, digestion, and our stress response. When the autonomic nervous system finds balance, the physical sensations are unmistakable: deeper breathing, slower pulse, a sense of groundedness that can be difficult to explain but impossible to miss.

When the body perceives 1/f fluctuation through the senses — through what we see, hear, feel, and smell in a forest — a cascade of responses may follow. According to the research of Japanese physicist Toshimitsu Musha, one of the key mechanisms is the stimulation of alpha waves (α-waves) in the brain.

You may have encountered alpha waves in the context of meditation or sleep. They are associated with a state of relaxed alertness — not drowsiness, not anxiety, but the calm, open awareness that most of us find very difficult to access during a normal working day. Alpha waves are the brain’s way of saying: I am safe, I am present, I can rest.

Alongside this, exposure to natural 1/f environments is thought to help regulate the autonomic nervous system — the part of our nervous body that governs heart rate, breathing, digestion, and our stress response. When the autonomic nervous system finds balance, the physical sensations are unmistakable: deeper breathing, slower pulse, a sense of groundedness that can be difficult to explain but impossible to miss.

There is a specific magic that happens in Hakone when winter transitions into spring. While most tourists flock to the sulfurous vents of Owakudani or the calm waters of Lake Ashi, those in the know head to the highlands of Sengokuhara. But on a specific weekend in April 2026, I didn’t go for the usual postcard view.

I was hiking up Mt. Kintoki (金時山) , the legendary peak named after the folk hero Kintaro. The goal was the usual reward: a breathtaking view of Mt. Fuji towering over the valley. However, what I witnessed from the summit was not just the iconic mountain, but a man-made inferno that painted the valley below in shades of orange and black.

From my vantage point, I watched the Sengokuhara Susuki Field burning unfold in real-time. It was a beautiful, and deeply meaningful spectacle. Thanks to my position on the mountain, I captured the event from a perspective few get to see—flames licking at the base of the hills while Fuji-san stood silent guard in the background.

In this post, I’ll share my experience, explain why Hakone burns these beautiful fields, and give you the exact details you need to witness this fiery tradition yourself.

What is the Sengokuhara Susuki Field?

Before we dive into the fire, let’s talk about what is being burned. Sengokuhara is a highland resort area famous for its sprawling fields of Susuki, or Japanese pampas grass (Miscanthus sinensis). In the autumn, this field turns a shimmering silver-gold, swaying in the wind like a sea of fur. It is so picturesque that it has been selected as one of the “Kanagawa Scenic 50” .

However, Susuki is a resilient and aggressive perennial grass. Without human intervention, these fields would eventually become forests. To preserve that iconic autumn landscape, the locals must act as stewards of the land—using fire as their tool.

The “Yamayaki”: Why Do They Burn the Fields?

If you visit Sengokuhara in late March, you might be shocked to see the ground charred black and smoking. Do not be sad; this is actually a sign of new life.

This tradition is known locally as “Noyaki” (野焼き) or “Yamayaki” (controlled grassland burning). Historically, the Susuki grass was a vital resource. During the Edo period (1603–1867), it was harvested for thatching roofs, feeding livestock, and making straw bedding .

However, as Japan modernized, the demand for Susuki vanished. By the 1970s, trees and shrubs began overtaking the marshland, threatening the unique ecosystem. In 1988, the preservation movement successfully resumed the controlled burns to stop the forest from reclaiming the grassland .

Today, the burn is a deliberate conservation effort with three specific benefits:

1. Preventing Forest Succession

Without fire, Mt. Daigatake’s forests would send seedlings down into the plain. Within decades, the beautiful open fields would become dense woodland. The fire resets the clock, killing tree saplings while allowing the deep roots of Susuki to survive.

2. Nutrient Recycling

Volcanic ash is incredibly fertile. Burning the dead winter foliage instantly returns potassium and minerals to the soil, acting as a natural fertilizer for the lush green shoots of April.

3. Pest Control

The intense heat eliminates overwintering insects and parasites, ensuring a healthier ecosystem for the flora and fauna that thrive in the following months.

The 2026 Burning: A Date with Fire

The burning is typically held mid-to-late March, usually on a dry, windless Saturday or Sunday. In 2026, however, it happened on a weekday in April and I happened to be on the trail during the event.

When I went: mid-April 2026.
Where I watched from: The summit trail of Mt. Kintoki.

From the trail, the sound is the first thing you notice—a deep crackling roar. Because the field is closed to the public during the burn for safety (no one is allowed inside the area), the best way to view it is from above. The local fire brigades and farmers methodically set the fields alight. You watch the fire rush up the gentle slopes of Mt. Daigatake, consuming the dry beige grass in seconds, leaving a stark black canvas behind.

Where to View the Sengokuhara Burning (Best Viewpoints)

If you want to see this event in the future, you need a strategy. You cannot stand in the field when it is burning. Here is the best location:

Mt. Kintoki Trail (The Hiker’s Choice) – RECOMMENDED

This is how I viewed it, and I highly recommend it. The Mt. Kintoki trailhead starts near the Sengokuhara area. The hike is moderate (about 1.5 to 2 hours to the summit). From the top, you get a bird’s-eye view of the entire field below with Mt. Fuji in the background. Pro tip: Start your hike early so you are at the mid-to-upper slopes by the time the fire starts.