Koto is the referee in the Dark Tournament. She is a fox demon like Kurama, but seems to have no special abilities. She is later replaced by Juri and switches to commentary. She was also the referee in the Makai Tournament. She is an idol in both the human and demon planes. She seems to have a crush on Kurama's demon form, Yoko.

Koto often seemed overly amused by the suffering of the fighters in the Dark Tournament, leading to her looking like a mean character. However, she later reveals that she can only enjoy brutality when both contestants can fight back. During the tournament, she begins a ten-count in an attempt to stop Bakken from beating up Kurama- showing that she is not totally sadistic. She also has the entire tournament rule book memorized.

Koto is briefy the object of affection for Chu, whom she doesn't share feelings for. She sometimes puts on a cute act, but is very shrewd and manages to get in jabs at Juri being a former 'cocktail waitress'.