Ebino Plateau is really near where they are... Like they seem to be at the fork with the 1st and 30th prefectural road where is located Ebino Plateau.
Ebino Plateau here:
https://maps.app.goo.gl/91YsNHCrCCns9VQr8
But yes the Fudo Pond is in the continuity of the 1st prefectural road, so they will miss it if they follow the 30th.
Fudo Pond:
https://maps.app.goo.gl/Axbp5idBRFcMjWVB8
I can't find where is Sanzu River though...
While the name of the establisment is not showed, I'm 98% sure this is the place (look at the pictures of the bath):
https://maps.app.goo.gl/fq3PApR13Ydq26HJA
Between Onanimo Pond and the hotel there is 10 km!!
I think they began the day at Kagoshima, slept in the tent between (the color page from the previous chapter) and this is the end of the second day. So in two days (Kagoshimo to the hotel) they travelled 80 km!!