Recently completed a stay here, and I echo the sentiments above that this is an excellent property. The shuttle bus from the station is easy to find if you arrive at Kagoshima Airport and take the bus to the station, as the bus stops are right next to each other. If arriving on the train, may be a little harder to find but just look for the bus stop signs at the station and it is on the lower level off to the side a bit. The bellmen were fantastic at this property, as is usually the case in Japan. Check in was pleasant and brief while still going over benefits and some other details. Concierge team was excellent and helped get me some day passes for traveling around the city. I particularly recommend the Chiran Peace Museum (an old military base that was the final departure point for many kamikaze pilots), about an hour south on a bus. Not much in English at the museum, but it is very moving and powerful nonetheless to see the pictures and read the final words of the hundreds of pilots.
Room: I had the Sakurajima King room, must have been a corner version of it because the website pictures don't have the big windows that I had (the windows I had were pretty much across the entire room and even wrapped a bit onto the side with the bed). Excellent room, although the shower set up could be a bit awkward for some as to get to the toilet you walk right past the sink and shower. The partition does block the view of the shower from the bed though. Shower pressure was excellent and temperature was good as well. Toilet was of course a nice Toto one, although a bit surprising for a new, nice hotel that the lid did not open automatically (true first world problems, lol). The bed was comfortable and I liked the daybed by the window. Very spacious room and the view truly is remarkable. I got there at night and my jaw dropped the next morning when I had a (mostly clear but not fully) view of Sakurajima. One of my favorite ever views in a hotel room.
Food: Had room service the first night due to fatigue and quality was good with excellent service as you'd expect. English was a problem but nothing Google Translate couldn't help with. I thought the breakfast spread was solid in the restaurant (did not have lounge access), although it is certainly busy with lots of families. Ate the rest of my meals in the city, I can recommend Ichi-Ni-San Kagoshima (Main Store), a short walk from the hotel. Excellent food with a good staff that spoke some English and English menus. 3.65 on Tabelog.
Service: As you'd expect in Japan, excellent with some language barriers. Most staff did not speak any English, but the front desk and concierge spoke it well.
Onsen: Used it a couple of times. Very nice facilities, although this was my first time so no ability for me to compare to other places. Not much to say here, but if you're on the fence about it or have never used one before, it is a pleasant experience that is nowhere near as awkward as you may think it will be. Just make sure to know the basic rules before hand (and that goes for any onsen in Japan).
An interesting note, I did not see any other Westerners, at least it was not obvious as I did not hear any English or see any obvious Europeans/North Americans. Client base seemed to be mostly Japanese with tourists from South Korea and China. That goes for the city/region as a whole too, virtually no other non-Korean/Chinese tourists over the few days I was there. After visiting Hiroshima and Tokyo later in the trip, it became very clear that Kagoshima and Kyushu are a bit off the main tourist road, which I actually really appreciated and enjoyed for a change of pace. I'd like to go back to the region and explore more.
TLDR: Overall, an excellent property. Highly recommended.