Kagoshima resident Turner has blogged a trip to the island of 硫黄島 (Iôjima). Not the island that was a battlefield in the war, but part of the Mishima village island group. The photos of the hot springs make it look like a fantastic place to visit, if you’re in Kyushu with time to spare.
Added bonus: the island group also contains a 竹島 (Takeshima), in case you needed any more potential geographic confusion. I guess it’s only to be expected that this country would have multiple places named “bamboo island” and “sulfur island.” Japan is all about the volcanos and bamboo and stuff.