Katsuo is a donkkaseu restaurant in Seoul serving hirekatsu and roseukatsu. Hirekatsu uses tenderloin, while roseukatsu uses sirloin, and either can be ordered as a set with udon. Orders are placed at a self-service kiosk, and meals are eaten in a narrow bar-style space. The udon is topped with a large amount of fried batter, which makes its taste disappointing.