Onioshidashi Park
鬼押出し園
A field of black lava in Tsumagoi, Gunma, left by Mt Asama's great 1783 eruption. Walk paths between the lava rocks with the volcano right in front of you.
A lava field born of the great Tenmei eruption
Onioshidashi Park is a visitor attraction at the northern foot of Mt Asama in Tsumagoi village, Gunma Prefecture, inside Joshin'etsu Kogen National Park.
In 1783 (the third year of the Tenmei era), Mt Asama erupted violently. The lava that flowed out at the very end of that eruption is the Onioshidashi lava, which ran about 5.5km north from the summit in a stream 800 to 2,000m wide before cooling and hardening. The landscape of jagged black rocks piled up as far as the eye can see was born at that time.
A name meaning "demons pushed out the rocks"
The name is said to come from the people who witnessed the eruption, who felt that "oni (demons) were raging in the crater and pushing out (oshidashi) the rocks".
In this eruption, Kanbara village at the foot of the mountain was swallowed by an avalanche of debris and 477 people died. It is said that 93 people who were at the village's Kannon hall survived. In the park stands the Asamayama Kannon-do, built in 1958 as a branch of Kan'eiji temple in Ueno, Tokyo, which honours the victims of the eruption.
Walking among the lava
The park has walking routes that take you past its sights as you weave between the lava rocks. You can see the "Ishiwari no Matsu" (rock-splitting pine), a pine of over 100 years old that has grown with its roots in a crack in the rock, as well as patches of luminous moss (hikarigoke).
From around May, all sorts of alpine plants flower between the lava rocks. Allow roughly 30 to 60 minutes for a visit.
Getting there
It is about 40 minutes by bus from Karuizawa Station on the Hokuriku Shinkansen. Buses also run from Manza-Kazawaguchi Station. By car, it is about 45 minutes from the Usui-Karuizawa IC (interchange) or about 50 minutes from the Komoro IC.
The park is open all year, but depending on the season the opening period and hours may change or it may close. Check the official website before you go.
Tips
- The lava paths are rough underfoot, so wear comfortable shoes. Wheelchairs and pushchairs can be borrowed free of charge.
- There is a dog run where you can bring your dog.
- In the park you can also try painting an oni (demon) money box.
- On the building's second floor there is a restaurant with a view, where you can look out over the lava field while you eat.
Sources
Updated 29 September 2026. Opening hours and prices change, so check the official site before you go.
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