Exploring Unzen Onsen, One of Japan’s Best Hidden Hiking Hotbeds

Japan isn't the kind of country to give away its secrets too readily. It's a special place that begs for multiple visits, where you’ll never leave feeling satisfied that you "clocked" the whole country.

After living in Tokyo for seven-plus years, I've realized that if you think you know a lot about Japan, congratulations, you're well on your way to realizing you have so much more to discover. Places like Unzen Amakusa National Park first inspired me, formerly a non-hiker, to get out into the mountains and explore the incredible landscape of this enigmatic country. Soon I learned that Japan is a ridiculously excellent hiking country. The trails are lovingly cared for, the backcountry huts on top of the country's highest peaks offer superb cuisine and facilities, and you can travel with peace of mind knowing the routes are safe but still challenging (and free of poisonous critters, unlike my home country, Australia).

The sheer abundance of accessible trails inspired a few local friends and i to start a hiking club in 2022 called Open Country, where we take folks out into the mountains—predominantly around Tokyo—to help them feel confident about hiking themselves in the hopes they later go off on their own independent journeys and get to know the country, its unique peaks, diverse landscapes, and fearsome volcanoes a little more intimately.

If you’re a nature lover with a spare few days looking for a real, authentic slice of Japanese life, a few mountain ranges to frolic in, a bit of volcanic-fueled adrenaline, and enough (cheap) onsen options to keep you pruney for days, Unzen is a no-brainer. Read on for the full local’s guide.

What to Know About Unzen Onsen

Located in Nagasaki Prefecture, Unzen Onsen is a small, unpretentious onsen (hot spring) town set within the boundary of Unzen Amakusa National Park, Japan's first designated national park in 1934 (fun fact: 2024 marks the park's 90th anniversary). Despite being a popular local destination for hiking and natural onsen, this deeply beautiful locale is often overlooked by travelers and tourists.

Unzen Onsen is also the name given to the volcanic water source that rages through this mountain and is pumped through a network of pipes down into the town's bathhouses and traditional ryokan inns. In the early 1900s Unzen was adored for decades by the local population of Japan and once wealthy foreigners (predominantly Western) vacationing from China, though it has long since dipped from global recognition. But the almost-forgotten nature of it all makes it undeniably so much more special.

The township today is humble; a morning stroll through the main streets will give you a pretty clear lay of the land. There's a single convenience store (not even one of the big three: Lawson, Family Mart, or 7/11), a handful of local guesthouses, a slightly bigger handful of onsen resort hotels (done tastefully, it’s worth noting), and a population where the average age of 70, at least.

Unzen Onsen is cute, compact, and culturally unique, but it's also super low-key, and that's really the charm of it.

The Fiery History of Mount Unzen

Overlooking the town of Unzen Onsen is Mount Unzen, an active stratovolcano that’s part of the Unzen volcanic region, which features a complex of several overlapping volcanic cones. Known as one of the country's most active and dangerous volcanoes, Mt. Unzen has a history of eruptions, the most destructive being the 1792 eruption, which tore through the landscape and triggered a large tsunami, resulting in the unfortunate death of upwards of 15,000 people.

Mt. Unzen was most recently active between 1990 and 1995, with a large eruption in 1991 being featured in the spectacular 2022 National Geographic film Fire of Love. In a final scene, pyroclastic flows and mudslides raced down the mountain, stealing more lives, including (spoiler!) those of the film's charismatic subjects, volcanologists Katia and Maurice Krafft. Though devastating, the eruption created Japan's newest mountain peak, Heisei-Shinzan. And while this new peak is only open occasionally—mainly for scientists, local university students, and journalists—visitors can get close enough to see the swirls of sulphuric gasses still emanating through the ground from nearby Mt. Fugendake.

Despite its deadly reputation, the mountain and the volcanic area that lay below the peaks and their subsequent onsen have long been too irresistible to ignore.

My hot take on Japan is getting to know the country via its mountains is one of the best ways to experience its diverse and beautiful culture, and this is coming from someone who never climbed Mt. Fuji. In fact, even hotter take, there are probably 100 mountains in Japan worth climbing before even considering Mt. Fuji. To start this list, we’ll kick it off with Unzen.

The Best Hiking Trails on Unzen

At 4,458 feet tall, Fugendake is one of Unzen's main peaks. It is a popular destination for those who want to get close to its formidable neighbor and see the towns sprawling out to the sea below. A practical point, if you're visiting from overseas and are relying on AllTrails to navigate your way around (local tip, YAMAP is the Japanese and much more detailed equivalent), then Fugendake is also the best recorded and well-marked.

Before trekking up the mountain, it is worth swinging by the Unzen Visitor Center in town to pocket a few loose maps and collect some pointers from the local experts. Conversations with locals, experts included, may require a little Google Translate if you don’t speak Japanese, so get that data roaming. The trailhead starts from near the car park and is situated a short drive up the mountain. To get there, punch "Nita Pass" into the GPS.

As you head up the mountain, one major trail splits off as you get close to the peak, although it's an out-and-back route. There are little backroads, routes for locals, and one key route that gets you to the top. A note: according to Uznen locals, the parks put in a few small "toilet trails" that shoot off the main track to offer a little public privacy when nature calls. You should not be adventurous and assume these unmarked trails are secret trails because, according to the local park rangers you wouldn't be the first person to get lost. I was told that a man called the police after thinking he was lost, but he was only about 20 meters from the trail. As you can assume, it was talk of the town for a week or so.

The difficulty level of the hike can vary depending on the routes you decide to take, but it is generally considered to be moderate to challenging. The biggest challenge is uneven terrain, steep slopes, and dipping clouds that can impair your views.

Legth-wise, though, it's what the Japanese would call "asameshimae" (translate: "a piece of cake" or more literally "before breakfast" as in it's so easy you can get it done "before breakfast." Leave by around 10am and you'll make it for lunch up top.

When to Visit Unzen Amakusa National Park

Given its position down south, at the warmer southern end of the country, Nagasaki is a pretty mild place to visit year-round, and Unzen is similarly pretty much open throughout the year.

Spring is peak cherry blossom time, but it is also most likely one of the busiest times of the year. Summer brings lush greenery and a little more humidity than you might be used to, but that's all part and parcel of Japanese summers. Autumn is arguably the best time to go, especially as the days get a little cooler and that end-of-day onsen levels up in appeal.

Also, it's worth noting that around October and November, which is the harvest season in Japan, the local produce is in a new range of deliciousness, thanks to the volcanic mineral-rich soil. Winter might bring a little dust of snow, but if you're ok with the cold, it's worth a visit around then to see the small ice flowers that form on the mountain's foliage.

How to get to Unzen Onsen

If you're traveling from Tokyo, then the best jumping-off points are Nagasaki or Fukuoka cities, both vibrant cities in Japan's southern end with their own unique charms and cultures.

From Nagasaki City:

Take the JR Kyushu Limited Express train to Isahaya Station. Then, transfer to the Shimatetsu Line at Isahaya Station and ride to Unzen Station. From there, you can take a bus or taxi to the onsen area.

There are some direct local buses from Nagasaki Station to Unzen Onsen.

From Fukuoka:

Take the JR Kyushu Limited Express train from Hakata Station to Isahaya Station, then transfer to the Shimatetsu Line to Unzen Station. After arriving at Unzen Station, proceed by bus or taxi to Unzen Onsen.

Some bus companies offer direct services from Fukuoka to Unzen Onsen, but the schedules may be limited, so it's worth doing a little Google Map research.