Daytrips from Kurokawa Onsen or alternative?

I'm planning to stay two nights in Kurokawa Onsen in May this year. Originally I wanted to use the second day to do a Daytrip to Aso Mountain but seeing it's still closed off I need alternatives.

The planned route in that area is: Yufuin Onsen (1 Night), Kurokawa Onsen (2 Nights), Kumamoto (1 Night)

Are there any worthwhile daytrips from Kurokawa Onsen by public transport? Alternatively where else could I spend my second night instead of Kurokawa Onsen? (I'm in Yufuin Onsen before coming to Kurokawa and will travel to Kumamoto afterwards)
I looked into the Aso area but couldn't find any interesting place to stay...

Using public transport - the answer is no.

Take a day away from Kurokawa and add it elsewhere.

Kurokawa is a charming small onsen town, but there is not much else besides onsen. One night is sufficient to experience Kurokawa. Have you or are you planning to visit Beppu? Beppu is an onsen CITY. You can go to onsen in Beppu→Yufuin→Kurokawa and experience differences in scale, if you are willing to move 3 days in a row.

Generally onsen ryokan is expensive and many Japanese stay not for just sleep but for the onsen experience by itself. To this end, we (the Japanese) arrive early, like 14:00, take onsen twice before dinner and after that take onsen and again take onsen before sleep. Next morning take onsen when wake up and before and after breakfast. Of course stroll around the ryokan is also nice.

For this type of onsen experience you don't need to go to other places, but you can enjoy onsen and stroll for almost 2 full days. Kurokawa is nice place for onsen experience.

I agree with Frog above.

In the full day that you have in Kurokawa, you could always enjoy a really nice walk around the village and visit some of the other ryokans to try their baths (using the cute discount pass). That can be done easily on foot, and some of the outlying ryokans are in nice scenery. If you want to really relax, this could be a fantastic two days of slow luxury...

Meoto falls, maybe? I haven't been there, but it looks like there is a bus connecting it to Kurokawa onsen.
https://maps.app.goo.gl/ekdjYPH8GYpioUwh9

@H
wrong, there is a Bus that also goes to Kuju mountains, which I will probably do instead of Aso. The only downside is that there are only 3 buses per day and they require reservation, so I can't decide spontaneously.

@frog1954
I know, I have been to onsen before. One day will be spent like that but the second day was meant to use as a daytrip somewhere else and in the evening relax in onsen again. Kurokawa is small enough for one day.

@ITO I was in Beppu before and I didn't like it. It's just an ugly city, not a cute town.

One night is enough for Kurokawa Onsen - get the tegata ticket and visit 3 places there during the day besides where you'd stay. There are around 30 places there, and they range from excellent to just OK. Some of the best are on this site's page:
https://www.japan-guide.com/e/e4575.html

As for day trips from Kurokawa there is nothing really convenient by bus - there is the Kyushu Odan Bus to Aso which takes almost an hour. But the whole Aso area is best seen by rental car - there are several good places if driving, otherwise...

Kurokawa is a great place famous for its outdoor forest onsen. Lots of places in Japan have a high wall around you for gender privacy. But there are not very many places with no wall at all - just a forest around you, which is pretty cool.
https://youtu.be/Xs_JXC6bhkM

If you cannot or ain't willing to drive. Don't expect many options. Have fun in the Kuju Mountains with you 3 round trip buses available. Dunno why you ask questions only to tell people they are wrong.

Thanks for the negativity.