Kuwabara's bosozoku-esque outfit.
A bōsōzoku (暴走族/ぼうそうぞく, lit. "rampaging clan") is a type of Japanese biker/thug gang. Members are said to wear long white military coats, and wear their hair in a stereotypical yankii (hoodlum) pompadour. They are often portrayed carrying bamboo kendo swords, fitting as Kuwabara himself is a swordsman. Kuwabara's outfit in the Dark Tournament, as well as his hairstyle in general, and to a lesser extent, his behavior, draws heavily from this trope.
Yusuke himself is dressed in such fashion on the cover of the third manga volume.