It's this 'title' some of the bigger name oni used to have. Four of them from a major mountain. Old drinking buddies and trouble makers. They still kept in touch.

Suika was always a disrespectful, arrogant one without a care in the world. Yuugi... just likes to be free to live her life on her terms. I think Suika liked to wander more. She and I don't get on great. [Snort.] Yuugi patrols the streets in hell. Keeps folks from getting too rowdy.

It's really an excuse to pick fights she thinks will be interesting.