Best Genist is a young man with light-colored hair. His mouth isn't visible because of his long collar which resembles jeans with a belt. In fact both his jacket and his pants seem to made of the same material as jeans pants. He also wears light-colored shoes.
Nothing is known about his personality.
Katsuki's workplace of choice is revealed to be Best Genist's hero office. In the office, Best Genist deduces that Katsuki chose him and his office because he ranks among the top five Heroes. Katsuki replies that he nominated him, to which Best Genist says he did since the other candidates have been good kids and it has been a while since someone like Katsuki has come along, telling Katsuki that reforming brutish people is what he does as a Hero. Best Genist tells Katsuki that he will show him what it is that makes people Heroes.