Hikoichi Yakou  

, 夜行 妃古壱

In the manga Usogui, Hikoichi Yakou is Referee #2 in Club Kakerou and one of the oldest referees there. Besides officiating games, he's known for his skills in collecting debts. He goes by the nickname "Debt Collector". His twin brother, Jouichi Yakou, is also present in the series. Hikoichi is exclusively assigned to Madarame Bakus matches as a referee.