As his name implies, Kurogiri's entire body is made out of a dark purple mist, save for his eyes, which are glowing yellow. He normally wears a very elegant suit with a tie and has a metal brace that goes from around his collarbone to just below his eyes.
In his villain costume, he covers himself in his dark fog, with only the metal brace around his neck being visible.
After being re-awakened from his imprisonment, his body has some alterations with more elements of Oboro becoming visible.
DAD.