>>35777491In the final game Firebreathers are still dressed like clowns and you mostly find them in caves
The demo map has a tropical area and there's location data for a "Mt. Fuji." These things fit fine in a tropical coast area, especially a volcanic one (no shortage of volcanoes in Japan), or they could literally swim in a magma sea and make their balls out of lava.
Somewhere like One Island/Mt. Ember in FRLG would be a perfect spot to find them.