Kumamoto o Aso to Kurokawa onsen and back

Hello, i need help. I will do a trip to Japan in oct/nov and i can find the way to reach kurokawa onsen. Really i explore this page http://www.kyusanko.co.jp/ up and down but i dont understand the timetable neither the way to reserve it. Can anyone help me? I will stay in nagasake 2 days and then go to kuragawa for 1 day and then return to tokyo. Plaseeee

In order to go to Kurokawa Onsen from Nagasaki, it is necessary to go through Kousoku Kiyama Bus stop, Hita St. or Kumamoto St..

I write the timetable if you switch in Kiyama bus stop.

Nagasaki - Kousoku-Kiyama - Kurokawa-onsen
7:30 - 9:23/10:07 - 12:04
12:30 - 14:45/15:00 - 16:57

The reservation of the high-speed bus is possible from one month prior to the travel date. The bus to Kiyama from Nagasaki seems bookable on the web, but, Kurokawa Onsen bound can not seem on the web of the English version. I think it's possible by phone to Kyushu express bus reservation center.
http://www.atbus-de.com.e.jo.hp.transer.com/howto/yoyaku-phone/

Fukuoka - Kiyama - Hita St. - Kurokawa-Onsen Bus Time Table
http://www.kyusanko.co.jp/sankobus/toshikan/kurokawa/table/tt1.html

Please note if you change buses at Kiyama, it is necessary to walk to the bus stop in the opposite direction.
http://www.atbus-de.com.e.jo.hp.transer.com/terminal_list/busstop-kiya...

I am glad to answer to your question as a Kumamoto resident.
1. From Nagasaki to Kumamoto
1.1 Train
You can find a way from Nagasaki to Kumamoto by train at www.hyperdia.com.
1.2 Bus
The bus time table from Nagasaki-ekimae (Nagasaki Station) to Kumamoto Kotsu Senta (Kumamoto Transportation Center):
Nagasaki 7:40 9:10 11:10 13:10 14:50 16:10 17:40 19:10
Kumamoto 10:58 12:28 14:28 16:28 18:08 19:28 20:57 22:27 3700 yen
For reservation, call 096-354-4845 or 095-823-6155(Japanese only).
I suppose you can buy a ticket at Nagasaki Station.

2. From Kumamoto to Kurokawa-onsen
The bus time table from Kumamoto Kotsu Senta (Kumamoto Transportation Center) to Kurokawa-onsen.
Kumamoto 8:04 9:04 12:15
Kumamoto Airport 8:57 9:57 13:08 800 yen
Kurokawa 10:44 12:26 15:37 2060 yen
For reservation, call 096-354-4845 (Japanese only).
You can buy a ticket at the Kumamoto Kotsu Senta.

3. From Kurokawa-onsen to Kumamoto
The bus time table from Kurokawa-onsen to Kumamoto Kotsu Senta (Kumamoto Transportation Center):
Kurokawa 10:35 15:20 16:25
Kumamoto Airport 12:35 17:49 18:25 1750 yen
Kumamoto 13:12 18:26 19:02 2060 yen
For reservation, call 096-354-4845 (Japanese only)
You can buy a ticket at the Kumamoto Kotsu Senta.