Hotel Pemandian Air Panas di Aso District

An absolutely wonderful experience.
The staff at the ryokan were incredibly polite and always ready to help with anything we needed. Upon check-in, we were provided with traditional attire, pajamas, tabi slippers, bath amenities, and a small welcome treat with matcha and coffee. We also asked at the front desk if they could give us a ride to the bus stop after check-out, and they kindly said yes, of course. 
Our room was spacious, clean, and beautifully decorated. At first, we were planning to explore several other local onsens, but after experiencing the ones at the ryokan, we felt completely satisfied. There are separate baths for hotel guests (men’s and women’s), baths open to both guests and visitors (also divided by gender), as well as a private onsen. One of the onsens also has a sauna.
The traditional dinner and breakfast were both impressive—delicious and very generous in portion.
The surrounding grounds are stunning, perfect for peaceful walks. This ryokan is a bit further from the main cluster of inns, but that was exactly what we wanted—to enjoy quiet walking.
At night, our futons were laid out for us, adding to the authentic experience. The only reason I deducted one star is the very bright green light on the ceiling that stays on all night and can’t be turned off or covered. I didn’t have a sleep mask with me, and the ryokan didn’t provide one, so I had a sleepless night. It was quite unpleasant.
That said, I still highly recommend this ryokan—it’s an unforgettable place to stay.

From entering the parking lot everything is taken care of, the rooms are enormous, the size of and amenities of a decently sized appartment along with a large kitchen and finally a private onsen fit for two people right next to the beautiful Kurokawa onsen river, aswell as a small waterfall creating an absolutely dreamy experience. The Ryokan is a about a five minutes walk outside the city center which is absolutely no problem as you have everything you need there. The gentleman in the reception speaks decent English so even with no japanese knowledge you should be fine They only seem to have four rooms, we got lucky and booked two days ahead, but most likely won't be that lucky. Absolutely would go again, great experience

It’s a good private house. But I’m won’t recommend if weather is cold or raining, or if you’re traveling with young kids. I travelled with my family with two toddlers. The bath and onsen are outdoors, not quite well lit and not well covered. The hot water water pressure is low, and the water is either very hot or very cold. It was a cold, raining and windy that night. It was a horrible experience for us because of the above, and the kids had a lot of trouble taking a bath. And we were worried they might catch a cold. And strangely the door lock of the bath is locked from the outside and not from the inside. Also remember to buy food before entering. We bought ours and cooked our own dinner. Otherwise, it’s a good private house, probably best for adults.