Map Location for one of quite a number of entry points into the park. There are many entrances.
One of the most famous natural areas near Tochigi is Oze National Park. This park spanning Tochigi, Fukushima, Gunma and Niigata prefectures features great wetlands, mountains, forests and a lake. Its quite crowded in Spring and Autumn. In fact it was fairly busy when we were there on a weekend in June. The park was originally part of the Nikko National Park, but was separated to form its own park to reduce visitor numbers to it fragile environment.
There is quite a bit of walking that you could do in the park. I would think you could easily spend 3 or 4 days here. But most people walk in and spend the night at one of the huts at the lake or in the wetlands and then walk out the next day. You can walk in via the mountain peak but I imagine that would be a fairly hard day if you're not fit.
Oze accommodation with a view
On our trip we walked into the wetlands on the first day. We did not book in advance and were able to get a room at the second place we tried. It looked like there were plenty of vacancies. I don't recommend this method. Had we failed to get a room it would have been a long, long day walking out again. The room was 8,500 yen each for the two of us in a small room with shared bathroom and simple dinner and breakfast. The staff spoke pretty decent English and there was a Chinese lady working there who spoke Mandarin.
Lots of boardwalks in the park
The entire park was really lovely. In June it was very green. It was also much cleaner than most Japanese walking destinations. I didn't see a single piece of rubbish on the ground the entire trip. The park was not crowded but it was definitely busy. Especially the area around the lake. I think for our trip there in Autumn when its more popular, we will have to go on a weekday.
Just a word of advice. Wear long pants! There are huge quantities of biting insects in the wetlands. They don't fly more than 40 or 50 centimeters from the ground so your arms and face are safe, but if you are wearing shorts they will eat you alive.
Next time I'd also like to climb the mountain.
More photos from the park and the drive in from Tochigi.