This area is also quite close to Gunma Prefecture, we visited the Shibasakura park where there were medium/large fields of shibasakura. The shibasakura (flowers that grow close to the ground) bloom white and purple. The time I went was also very close to boys day, so there were many koinoburi decorating the area. The Shibasakura park also had a small strip where they were selling souvenirs (omiyage) and different kinds of food (try the sweet potato!!). The air (compared to hot Bangkok) is quite clean. In Gunma, we also went to Ikado where there is a stairway lined with shops and small restaurants leading all the way to the top where there is a temple. Theres also a small hot spring area to soak your feet in (bring a small towel to dry off) where the water is warm and you can see it running down the mountain. The view is beautiful as well, there are 365 stairs which overlook a large mountain range once you reach high enough elevation.
There are a lot of native Japanese in these areas, and I would recommend having some of the language under your belt. I was with my family, all of whom speak Japanese, and it was quite a lovely experience. Beautiful areas to see, but not the feeling of overwhelming hustle and bustle of Tokyo.