"群馬県に「尻焼温泉」なる温泉があるらしい。尻好きとして一度は訪れてみたい秘湯であります。2007.10月" - kakanat

In Gunma prefecture, there is a hot spring called "Shiri yaki" (lit. "burn one's buttocks.")
As a man who likes asses, it is a secluded hot spring that I would like to visit once.
October 2007 - kakanat

"The name originates from the curing of hemorrhoids by sitting on a stone heated by the hot spring water that gushes up from the river bottom." from Wikipedia