Kumamoto Prefecture (熊本県, Kumamoto-ken) is a great place to go to if you’re looking for hot springs; they’re everywhere, including the popular Kurokawa Onsen. Be sure to visit Kumamoto Castle, one of Japan’s top castles, while you’re there as well.
If you like nature, Kumamoto is also a nice destination; Suizenji Park is perfect for photographs, while Mount Aso is one of the world's largest active volcanoes. Take a look at the unique Tsujun Bridge for some architectural magnificence.
One popular activity in Kumamoto is riding the scenic Steam Locomotive Hitoyoshi; make sure you get reserve seats well in advance, as tickets sell out surprisingly quickly. Kumamoto is also famous for its raw horse sashimi; if you can't muster up the courage to try that, have some tonkotsu (pork-bone broth) noodles instead.
Yamaga displays illuminated paper umbrellas and and bamboo candles on winter evenings in February.
The slopes of Mt Aso are alight with flames during the annual March fire festival.