This idea popped into my head recently.

To avenge his girlfriend's honor, a young man has to face a futanari girl in a cockfight. With hands bound behind their backs, they slap, press and rub their equally large cocks against each other. First to ejaculate is the loser

I picture the man just barely winning after several close calls. He then gets some sexual reward, like a boob job, from his girlfriend.

Anyway, I just wanted to get that idea off my chest. If anyone out there wants to make this into an actual story, they my blessing to do so.