Gunma is most popular for its renowned onsen towns, considered some of the best in Japan, as well as its breathtaking scenic peaks, which are suitable for beginners and less challenging than the Japan Alps. It's an ideal destination for those who enjoy relaxing hikes combined with rejuvenating onsen experiences.
For this itinerary, having a rental car is highly recommended to ensure maximum convenience and flexibility. The top choices for rental cars include Nippon Rental Car, Toyota Rental Car, Nissan Rental Car, Budget Rental Car, and Times Rental Car. I usually book from Rankuten Travel: https://travel.rakuten.com/cars/