(For the record, I think only TRC!Fuuma would be ballsy (lol) enough to go commando. But he probably wears boxers cause.)
lol have no clue what X!Fuuma would wear. It's a mystery~*
And idk what little!kuro does in bizarro!Japan, especially since he's pretty adverse to other styles of clothing (he's not as fashionable as his older self, haha.)
Boxers for: TRC!Fuuma
Briefs for: Ran, and little!cloney (but like JL said, if they have that kinda stuff in Clow Country.)