Travel to Kurokawa via Mt Aso by bus.
Kurokawa is a charming town, lined with ryokan, cafes, shops and small shrines. The ryokan are renowned for their outdoor baths, which allow you to take in the scenery while you bathe. Kurokawa offers an Onsen hopping pass, the 'Nyuto Tegata' which lets you visit three hot springs for only 1300yen (roughly £10), we highly recommend you take advantage of this!
Along the way, you will be passing Mt. Aso, an active volcano where you can visit the crater itself! This is a unique opportunity!
Depart Kumamoto at 10:46, arrive Mt Aso at 12:46
Spend a couple of hours exploring Mt. Aso.
Leave Mt. Aso at 14:16, arrive Kurokawa Onsen at 15:31
Enjoy your stay in a ryokan! If you've not tried out an onsen yet, now is definitely the time! Dive in! (Not literally, the water is relatively shallow.)