We had plans to stay at IC Beppu probably 3 times and it never worked out (2 trips due to Covid). Now considering a trip late 2022, so just checking out options. Actually, only been to Fukuoka airport once, but never spent time in Kyushu so I guess it's time (we've been to Hokkaido 7-8 times on the other hand).

Kai is the Ryokan brand for Hoshino Resorts who often do a slightly more modern take on traditional Ryokan, all usually quite upscale (aka costly). A bit like Tsugaru Group in Hokkaido though Hoshino have properties across Japan under various brands. IIRC, they opened a Kai Beppu in July of this year, but Kai Aso is a bit more remote and smaller / more exclusive. Often they offer in room onsen which we prefer (so convenient, haha).

On a side note, what's a good duration for IC Beppu (and maybe Beppu area in general)? Thinking of 3-4 nights with relaxation the primary goal and probably will rent a car while there for some flexibility / freedom. Any tips are appreciated. Thanks.