Kojigoku Onsenkan covered in thick fog
The moment we arrived, thick fog covered the area! This mysterious vibe instantly boosts the “hidden hot spring” atmosphere.

Hello! I’m “Mama Usa” (Mama Bunny), and I’m absolutely obsessed with hot springs and delicious food!! 🐰♨️

If you’re planning a weekend getaway and thinking, “I want to visit Unzen, but there are so many hot springs! Where should I go? And I want to eat something tasty too!” — look no further.

Today, for those of you drawn to that classic, rustic wooden building you’ve seen in photos, I’m sharing my real experience at Kojigoku Onsenkan in Unzen Onsen, Nagasaki. Plus, I’ll reveal my ultimate plan: “Set up your food to steam before bathing, and eat a glorious gourmet treat right after you get out!”

What Kind of Place is Kojigoku Onsenkan? Love at First Sight!

Overall view of Kojigoku Onsenkan and parking lot
A wide view of the facility. The parking lot is quite spacious!
Front of Kojigoku Onsenkan
The black octagonal roof. The nostalgic vibe is exactly like the photos!

The moment you step out of your car, the pungent, sulfuric scent of the hot spring tickles your nose. Right before your eyes is a wooden building that makes you feel like you’ve slipped back in time. Modern super-sentos (large public bathhouses) are great, but the “hidden hot spring (hitou)” vibe here is on another level.

This is a day-trip hot spring where you can enjoy 100% pure, unadulterated, free-flowing milky white sulfur water drawn directly from the source just behind the building. It’s a famous bath boasting a staggering 4.4-star rating (with over 1,100 reviews) on Google.

Signboard explaining the history and benefits of the hot spring
♨️ Incredible Water Quality & Benefits!
・Spring Quality: Simple sulfur hot spring (Hydrogen sulfide type)
・Temperature at source: 63.5℃ (146℉)
・Health Benefits: Neuralgia, fatigue recovery, poor circulation, cuts, and more!
It deeply soothes the shoulders and lower back, completely relieving the exhaustion from daily life and parenting ✨

My Experience: Like a Bathhouse Straight Out of an Anime!

Right as you enter, there is a reception desk with a staff member. On the left side, there’s a ticket vending machine. You buy your ticket there and hand it to the receptionist. It’s exactly the style of a traditional Japanese bathhouse (Sento) you often see in anime or dramas!

The shoe lockers are separated by gender, and the keys are made of wooden tags that you slide out to lock. Just seeing that gets you excited for the traditional experience.

【Mama Usa’s Fails💦】 Beware of the Dressing Room & Vending Machine Traps!

😭 Fail 1: Time your changing well!

The lockers are free to use, which is great, but the dressing room is honestly quite small. I like to take long baths, so when I was ready to get out, I waited for a moment when there were fewer people around my locker. A little mutual consideration goes a long way when it’s crowded!

😭 Fail 2: No drinks left in the vending machine!?

I was craving an ice-cold drink right after my bath, so I headed to the vending machine in the waiting area… only to find it was almost entirely sold out (´;ω;｀). The vending machines outside still had drinks, so if you definitely want a post-bath refreshment, I highly recommend buying one outside before you enter!

【Mama Usa’s Successes✨】 Hot Water, but the Kids Loved It!

✨ Great for kids who love hot springs!

Once you open the slightly stiff sliding door to the bathing area, you’ll find two pools of milky white hot spring water! The larger one on the right is the standard temperature, and the smaller one on the left is hotter.

Overall, the water here runs quite hot. There are no private family baths, so it’s not exactly a “kid-centric” facility. However, my 4 and 7-year-old sons are huge onsen lovers (I wonder who they take after?), and my husband reported that they thoroughly enjoyed it and said, “It felt amazing!”

After the bath, you can cool down in the tatami-mat waiting area behind the reception. The boys and my husband finished first and waited for me there, relaxing comfortably.

🇯🇵 How to Enjoy Onsen (Japanese Hot Springs)

1. Naked is Normal!

In Japan, we enter the bath completely naked. No swimsuits are allowed. It might feel shy at first, but once you’re in the water, nobody cares! Think of it as a liberating cultural experience.

2. Wash Before You Soak

The bathtub is for soaking, not washing. Please sit at the washing station and clean your body thoroughly before entering the shared tub. This keeps the water clean for everyone.

3. “Kakeyu” (Rinsing Water)

Before stepping in, rinse your body with hot water using the small bucket. It helps your body adjust to the temperature and prevents heat shock.

4. Keep Your Towel Dry

Don’t put your small towel in the bathwater. You can place it on your head or set it on the side of the tub. Also, long hair should be tied up so it doesn’t touch the water.

5. No Photos or Phones

Using smartphones or cameras in the dressing room and bathroom is strictly prohibited to protect privacy. Please keep them safely inside your locker.

6. Be Mindful of Others

Please use the shower carefully so water doesn’t splash on others. Also, an Onsen is a place for relaxation, so please keep conversations quiet and refrain from swimming or splashing.

7. About Tattoos

Historically in Japan, tattoos were associated with antisocial groups, so many Onsens still have a “No Tattoo” policy. However, rules are slowly changing recently.

💡 Tip: If you have tattoos, it’s best to ask the staff before entering, or cover them with skin-colored tape if they are small. Some places offer private family baths which are usually tattoo-friendly!

8. Dry Off Before Leaving

Wipe your body with your small towel before going back to the dressing room. This keeps the floor dry and prevents slipping.

Sightseeing Around Unzen: Unzen Jigoku & Spring Water

What is “Jigoku” (Hell)?

In Japanese, “Jigoku” translates to “Hell.” When visiting Unzen, you will see areas where intense white steam and boiling sulfurous water forcefully bubble up from the rocky ground. The strong smell of sulfur and the cloudy, steamy landscape look exactly like a scene straight out of Hell, which is how this area got its famous name!

Unzen Jigoku bubbling with steam and fog
Unzen Jigoku. The fog and steam made it hard to see everything, but the bubbling earth is spectacular!
Unmanned vending stall at Unzen Jigoku
An unmanned stall in Hell. This local charm is irresistible.

① Get “Jigoku Eggs” and Ramune at Unzen Jigoku!

When you say Unzen, you have to mention Jigoku! Although some walking paths are currently under construction due to past disaster recovery, it remains the main tourist spot. Here, you can buy “Jigoku Eggs (3 eggs per bag)” (eggs boiled in the hot spring water) and Ramune/Lemonade at an honor-system unmanned stall!

📍 See Unzen Jigoku on Google Maps
Jigoku Eggs
Ramune and Lemonade

② Fetch Some Delicious Spring Water!

While you’re nearby, why not collect some fresh spring water? Bring a plastic bottle or thermos, fill it up, and take it home. Using this water to brew coffee or tea at home makes it taste absolutely exceptional!

📍 See the Spring Water spot on Google Maps

▼ Click below to see the list


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Unzen “Jigoku Mushi” (Hell Steaming) – The Ultimate Plan!

What is “Jigoku Mushi”?

“Jigoku Mushi” (Hell Steaming) is a traditional cooking method unique to hot spring towns. It uses the 100°C (212°F) natural geothermal steam that rises from the earth to cook food. Because it cooks ingredients rapidly at a high temperature using natural minerals, it traps the umami (savory flavor) and natural sweetness inside. It’s an incredibly healthy, oil-free, and eco-friendly way to eat!

Right near Kojigoku Onsenkan, there is a public “Steaming Kiln” (Mushi-gama). As someone who loves both hot springs and good food, my absolute top recommendation is to set your ingredients in the steamer BEFORE you bathe, and eat the piping hot, delicious results right after you get out!

  • Fee: 250 yen for using the steamer (includes parking fee). If you only park without steaming, it’s 300 yen.
  • Payment: If the manager is absent, simply drop your money into the honor box.
  • ⚠️ CRITICAL RULE: Bringing meat or seafood is STRICTLY PROHIBITED! (This is because fats drip down and strong smells transfer to the kiln). Please only bring vegetables, eggs, or potatoes!
📍 See the Steaming Kiln on Google Maps
📖 【Related Article】 Guide to using Jigoku Mushi (Japanese)

♨️ Mama Usa’s Recipe: The Best Post-Bath “Jigoku Mushi” Ingredients

🚨 No Meat or Fish! Enjoy veggies and sweet potatoes that taste 100x better!
  1. Sweet Potatoes & Corn on the Cob (Put them whole into the steamer before your bath! When you get out, you’ll have incredibly sweet, fluffy, natural snacks ready to eat. The kids will go crazy for them!)
  2. Your Favorite Veggies (Broccoli, Carrots, etc.) (Steaming them in the hot spring steam condenses the vegetables’ natural sweetness.)
  3. Use “Jigoku Eggs” as a Dip! (Crush the hot spring eggs you bought at Unzen Jigoku, mix them with mayonnaise, and use it as a dip for your freshly steamed veggies… It becomes the ultimate dipping sauce! You’ll be completely satisfied even without meat ♡)

👜 Mama Usa’s Recommended Onsen Goods for Kids

If you visit an onsen with a small dressing room or no designated rinsing area, these items make the experience much more comfortable! These are must-haves for our family outings.

① Quick-Draining Mesh Spa Bag

A mesh bag where you can toss in all the family’s shampoos and towels. It drains water instantly, so you don’t have to worry about bringing it wet into your car. Keeping one in your trunk is a game-changer!

② Super Absorbent Microfiber Towel

Bulky bath towels are the enemy of traveling with kids! Microfiber towels fold up compactly but quickly absorb water from the kids’ bodies. You can dry them off in a flash, even in a cramped dressing room.

Basic Information Before You Go: Kojigoku Onsenkan

  • Address: 500-1 Unzen, Obama-cho, Unzen City, Nagasaki
  • Business Hours: From 9:30 AM (Please check the official website as hours may change)
  • Facilities: Shampoo and body soap available (also sold at reception). Hair dryers are available. There is no dedicated “Kakeyu” (rinsing tub), so use the small buckets or showers provided.
  • Parking: Available (Free)
  • Official Website (JP): https://www.seiunso.jp/kojigoku/
  • Map: View on Google Maps

Conclusion: Experience the Ultimate Onsen & Jigoku Mushi in Unzen!

Unzen’s “Kojigoku Onsenkan” is a fantastic hidden gem where the retro atmosphere and pure, free-flowing hot spring water will wash away all your daily fatigue.

Best of all, the bliss of setting your food in the steaming kiln before your bath, and biting into piping hot, sweet veggies right after, is an experience you’ll get hooked on! Why not plan a delicious and relaxing getaway to Unzen with your family or partner this coming weekend?

▶ Search for Hotels in “Unzen Onsen” on Rakuten Travel