Travel from Aso San to Takachiho

we are 2 adults and one child and are planning to travel from Aso San to Takachiho in May 2020. How can we travel using public transportation? How can we also go from Takachiho to Kagoshima? Can anybody suggest a good place to stay at Takachiho?

Pointless to start planning now; many things can happen in one year. Come back later.

Aso to Takachiho is very difficult these days by public transportation because some of the train lines are still not fixed from the 2016 earthquakes (and it was inconvenient even before the earthquake).

There is a bus that travels between Kumamoto and Nobeoka a few times per day that stops at Kumamoto Airport, Takamori and Takachiho along the way. One of the simplest way to travel from Aso Station or the summit of Aso to Takachiho would be by bus via Kumamoto Airport, but it is quite a detour, and both bus lines are very infrequent. If possible, I recommend to rent a car.

Kumamoto-Nobeoka bus:
https://kyushubusbooking.com/highway-bus/takachiho-go/

Aso-Kumamoto bus:
https://kyushubusbooking.com/highway-bus/kyushu-odan-bus/
https://kyushubusbooking.com/highway-bus/yamabiko-go/

Alternatively you could consider to travel via Ozu Station (aka Higo-Ozu Station):
Aso - (bus) - Ozu - (bus) - Takamori - (bus) - Takachiho

Timetable for the Ozu-Takamori bus:
https://www.kyusanko.co.jp/sankobus/community/minamiaso/

Takachiho to Kagoshima is much easier. Simply take the bus to Nobeoka (hourly buses: http://www.miyakoh.co.jp/bus/rosen/0_jikoku/6-01_20190401.pdf) and transfer to trains to Kagoshima.

Train timetable:
http://www.hyperdia.com/

Above information is unlikely to change by spring 2020. So, it is perfectly fine to start researching now already.

Thank you

We traveled through Kyushu about 10 years ago mainly by bus. We went from fukuoka to takachiho, to kurume, to kurokawa onsen , back to fukuoka, and then to yanagawa by train. We didn't go to aso san because it would have been inconvenient going there by bus. In takachiho, we stayed at takachiho hana ryokan iwatoya. It's located about a 5 minute walk from amanoiwato shrine which is why I chose to stay there. Because the ryokan in quite far from the town itself, when we arrived in takachiho, we visited the gorge and walked around the town. Later, the ryokan picked us up from the bus station and took us to the ryokan. The next morning after breakfast, they took us back to the bus station. (I don't know if they still do this.) At night, they take their guests into takachiho to see the kagura performance. I enjoyed staying at this ryokan. The food was good and their rates were inexpensive.

Thanks