Aso Nakadake is still an active volcano. When volcanic activity is quiet you can go near that crater. It is a rare place in the world.

You can see the activity status from the link below.

http://www.aso.ne.jp/~volcano/eng/index.html

It came to be called a couple waterfall because the two big and small streams fall together. From the village in Ogawa, you can see the beautiful figure over the rice terraces. You have to walk a little to get to the waterfall.

Zenzo Sakamoto is known as an abstract painter called "Gray Painter" or "The Oriental Silence". The work of Zenzo Sakamoto, rooted in the climate and nature of his hometown, has received high acclaim in the world for its unique abstraction in Japan.

https://sakamotozenzo.com/

In the quiet precinct of Shioi-jinja shrine is a spring pond that is deep and blue. Movement of water can be found only near the bottom of the pond. The water flowing from the pond is the only “Nonbori Gawa”, a river running eastbound, in Minamiaso. Its waterways are aesthetic.

https://www.minamiasokanko.jp/suigen-list/shioisha-suigen.html

The nature of Aso is protected by people. Noyaki controls insects that are harmful to humans and raises grass for cattle and horses.