Here’s a link to a page about Hitoyoshi Ryokan:

http://www.japanholidays.com.au/traditional-accommodation/japan-holidays-ryokan-collection/hitoyoshi-ryokan-hitoyoshi-kumamoto

This is the only hotel or ryokan in Kumamoto that I could find listed on the JapanHolidays website. It may be worth considering if your planning a holiday in the area.