Looking for cooler high-altitude camping spots near Tokyo

Hello! I’m looking for mountain/high-altitude camping spots to escape the summer heat. I usually go to Nagano, in the West Matsumoto area, but it’s around a 4.5–5 hour drive from Tokyo, which feels a bit rough for just a 2-day/one-night trip.

Does anyone know any cool camping areas closer to Tokyo that you’d recommend?

by broboblob