You might consider one in Nagano, Gunma, or Fukushima if you'd like to do an overnight. Compare it to the cherry blossom map and pick an area a little colder or warmer than Tokyo and Osaka to hedge your blossom bets.

My general feeling about Hakone https://www.flyertalk.com/forum/30287104-post3.html

Beppu... Beppu itself is like older Reno while Kurokawa is upscale carefully curated Colorado high end ski resort. They're not that far apart and Yufuin is also between them which is a cuter town with some shopping and sightseeing. I finally visited Beppu (an onsen mecca) and stayed in JR Kyushu Blossom Oita on top of the train station which was a great choice for me as I had a few other small onsen ryokan stays planned in the Aso region.