【English Ver.】Atosanupuri Trekking Tour blog

An active volcano, Mt.Io. Normally it banned to hike up. But you can explore with registered guides here. There is a English guide available, let us know in advance if you need.

What is Mt.Io? 

Mt.Io is called Atosanupuri(Naked Mountain in the Ainu language). Volcanoes which is in this area have been formed by an eruption that occurred approximately 7,000 years ago. The last eruption was phreatic eruption which was several hundred years ago, and its huge explosive crater is one of the highlights of the tour. Volcanic smoke is still pouring out from fumaroles even now, and the surrounding area is filled with the unique smell of sulfur. Many yellow sulfur crystals can be seen around the fumarole, and you can Feel the power of the earth from the sounds which are coming from the plenty of fumaroles!! Come to try this tour in Teshikaga(eastern hokkaido), Japan. It is totally worth it!!

The detail of this tour, which season should I pick?

Tour dates

2024.05.24 to 2024.11.03
※the end date would be determined based on temperature and snowfall conditions.
※Please book at least 3days before your desired date. we need time to coordinate the guide for you.

Time schedule


※afternoon tour will be changed to 12:00~15:00 due to the sunset time.

It takes 3 hours total. You can choose the starting time at 9am OR 1pm in the booking application.

Best time of this tour would be middle of June to begging of July. At this time, you would see the full of blooming of Ledum palustre which is white pretty flower 🙂

Tour price

※We don NOT accept below 12years old participant for the safety.
※Parts of tour fee will be used for the trail maintenance and enviromental conservation.

Atosanupuri Trekking Tour blog

【Stared from ‘Mt.Io MOKMOK base’ (souvenir shop)】

The guide explained about some precautions and we are on our way. Maximun 6 person for a guide. We go through nice flat forest for a while. It’s shaded and good for warming up yourself.

There are lots of flowers on the way. It’s pretty unique geology here due to sulfur. So feel free to ask your guide if you wonder about anything:) Also, this road was used by the Yasuda Railway for sulfur mining. The guide will explain about the history and you can listen some interesting stories! Small story..Yasuda’s great grandchild: Yoko Ono married Jon Lennon. Wow.

【walk through sulfur minig ruins】

From the above picture, you can see that two trees chewed a train rail and just grew together. It’s believed that it is from 60 years ago. But the rails are already even taller than my tall !! It’s crazy how fast the tree’s growth is.

It’s a short walk, but you can see the plats are changing every small section.

【Weather observatory inclinometer】

We gotta wear the helmet from this point. Also, the environment changed all the sudden. Forest to rocky area. Feel like I’m in the another planet. Pretty cool.

※We will give you the helmet in the beginning, so don’t worry!

【Sulfur minig ruins continue to here!

We pass though the remains of an old mining site. Due to the special soil containing sulfur, the trees are difficult to rot. So we still can see the some trees that used for the mining. Apparently there was a track coming here despite bumpy sketchy road. They were super tough!! It is not long long time ago, you can see some peace of the remains.

【The pipe for hot spring】

There was hot spring from a pipe! It was a bit hot temperature. Apparently, there are some people made the easy bath tab and enjoying the Onsen at this place. We can imagine it was must be great with this sensational views.

【Getting more fumarole!】

Be careful when you walk!Just follow the guide!

【The yellow crystal which made by plume】

You can not really see like this close !! It’s beautiful yellow color!!

【You can see the rail way here】

If you are lucky enough, you can see the train going through to the forest. The mountain on the behind is Mt.Shari. Small town with massive nature, Japanese rural views here.

【Finally, we are in explosion crater(called Kuma-Otoshi)!! 】

It’s magnificent!50meters depth! The name ‘Kuma-Otoshi'(meant ‘Falling Bear’) comes from the Ainu people who chased bears down this cliff. I guess it can be super hard to pull up the dropped bears after that…People are used to super tough!!

【’Kuma-Otoshi’ with ‘Koguma-Monaka’】

We have a break time here ! The guide gave us the cute treats. It is called ‘Koguma-Monaka'(baby bear Monaka). Monaka is Japanese traditional sweet with sweet red beans on the inside and two crispy wafers made from pounded rice on the outside. Bear Falling Explosion Crater with Baby Bear japanese sweets. Love this small treats!!

【Massive explosion crater with tiny people】

Can you see there are some people walking down the trail? These views made me feel like I’m walking the trail in US! We don’t really have this spectacular scenery in Japan. It’s just blew me up.

【The highest point of this tour: 337m】

You can see the parts of Lake Kussharo and the small town of Kawayu. Huge nature and small town make the beautiful contrast. Then, we are heading to the last point, F1 fumarole!

【F1 fumarole】

This is the biggest fumarole in Mt.Io. It’s always different beauty depends on the wind direction. Feel the sulfur smell and the smoke !!

【Going down the hill】

Going down to the Mt.Io MOKMOK base. It was pretty steep, whatch your step when you going down! lots of bush!! You can feel like an adventure 🙂

【The first Ledum palustre was blooming✿】

【Came back to the Mt,Io MOKMOK base】

Finally we came back! Good job guys!!Mt.Io MOKMOK base has ice cream, drinks, snakes etc. There is a cozy dining as well, so enjoy some treats for yourself after the big adventure : )

Our recomendation is the soft serve with caramel sauce and soft boiled egg. It’s called ‘Ontama-Soft’. You must try it!! It is really good !!

Enjoy your walk!
It is not only about the power of nature, you can learn about the history of sulfur mining and the unique plant ecosystem created by special soil, it was a very fulfilling trekking tour with lots of interesting things to see!! I’m happy to join this tour 🙂

Mt.Io is not too far from the town of Teshikaga, it is easy to join and guides are all knowledgeable. Some of guides are good at English so don’t hesitate to join us 🙂 Just let us know in the advance when you book this tour.

Teshikaga, Hokkaido, Japan. Surrounded by massive national park. Here is your next direction!!

You can jump to the booking information, tap below!

Official imstagram @atosa_nupuri

【Mt.Io MOKMOK base dining pic】

We are waiting you to join us!

Thank you for reading, Arigato!!