People are speculating Sabro, but Iruma and co. were directed to the owner of the place, not a participant. Participating in an underground fighting ring is Very Sabro, but running one isn't. He isn't really one for management. Considering the land of passion stuff, I could see it being Eliza! Maybe as a spin on her "every man is a suitor" thing, like now it's "every man is a champion."
Keroli is also a contender, her whole queen motif could easily put her in a management position. But also she's clearly still got the Hannah Montana "pop star double life" thing happening and "also by night she runs a bloodsport arena" might complicate matters a little too much?