When you go to Kagoshima, Kyushu Shinkansen is the best way to get there. It is fast and the trains come very frequently. But if you have a time, please consider the route from Kumamoto to Kagoshima-Chuo via Hitoyoshi and Yoshimatsu on Hisatsu line (肥薩線). It is very scenic route. JR Kyushu operate very attractive trains on this route.
Isaburo / Shinpei connects Kumamoto, Hitoyoshi and Yoshimatsu. This train is called as two train names but this is same train. The only difference is the direction. Isaburo runs from Kumamoto and Shinpei runs from Yoshimatsu. Both Isaburo and Shipei are the name of the key persons when the construction of this section was completed. Isaburo is the named from Isaburo Yamagata who was the minister of transportations and telecommunications. Shinpei is named from Shinpei Goto who was the president of Japanese Government Railways.
This train was operated as a local train between Hitoyoshi and Yoshimatsu. In 2017, one of two round trips started to run between Kumamoto and Yoshimatsu as a limited express train. Now this train runs as a limited express train between Kumamoto and Hitoyoshi, and runs as a local train between Hitoyoshi and Yoshimatsu.
Most of seats are reserved seat when this train is operated as even a local train between Hitoyoshi and Yoshimatsu. And this train is not just a regular local train but the cruising train. This train is operated by fully renovated sperized fleet. There is an attendant on the train. She shows you the scenery of Hisatsu line.
Hayato no Kaze is the limited express train that runs between Kagoshima-Chuo with Yoshimatsu. You can take this train by Japan Rail Pass with no extra charge. This train is the limited express train but this train is slow on Hisatsu line. Hisatsu line is very scenic route. This train is operated by specialized KIHA 147 series. The fleet of this train was fully renovated and it has very cozy Japanese atmosphere. The attendants are on board. They guide you about the scenery of Hisatsu line. This train stop at Kirishima-Onsen station. So you can take this train when you go to Kirishima mountains.
I will show you many images of this train and explain the details.