Punch her testicles

You decide to slowly remove her hands from where they were to her stomach and prepare your fist for the hardest blow you've ever delivered.

You brought your fist back and *BAM* "Auughhf!!!" Her poor exposed gonads could do nothing but take the hit and finaly, she woke up with whimpers and a pained facial expression, quickly cupping her balls with her hands in a foetal position while still as confused as before.

"Ugh.. W-what are you doing..?" She asked still half-asleep as you gently started tracing her bulge with one finger from up to down.

"Say, I've been thinking about it for quite a long while but how about we both had a busting fight ?" you ask with your confident and lustful expression but this doesn't help her sooth the pain away from her crotch.

"Argh.. Busting ?" She asked confused, so you gently made her lean back to the bed before answering her. "Basicaly it's your typical sparring session but there is a slight difference." You said as you slowly removed her hands from where they were and her sleepy state just lets you do so. "You have to crush your opponent sex in the process" You said as you swiftly punched her balls once more. She didn't even get to realise what was happening to her and her eyes went wide before closing instinctively her legs in pain.

"Ouch...Why...?" She asks pitifully while looking at you with one eye filled with a little bit of tear. But you know damn well that if there was someone crazy about sexual activities in this couple it was definitly her not you so you took the opportunity to ask her.

"Don't you wanna know how it would feel to hurt my sex once in a while ? You've been subjected to quite a number of unfortunate pain down there right ? I assume that you want to know how it would feel to be the dealer for once." you say while rubbing your crotch in front of her on purpose to influence her choice.

"Nnngh- sure but if anything I'd rather avoid to hurt you for that..." She replies slowly brushing the pain off.

"Do not worry about that, it JUST so happen that this kind of thing, turned me on, so would you be part of it ?"

"I don't know hun... It was really painfull..."

"Yet your dick seem to be throbbing quite a lot isn't it ?" You say knowing damn well that this was just a natural reaction to her genitals being touched but you just can't help yourself and want to hurt those balls so bad you're pratically drooling just from the thought of it.

And you're maybe drooling too much because your girlfriend noticed it and let out a little sigh knowing that you would definitly not back down from that, and gave in.

"Fine, I'll give it a try then"

"Yes ! Thank you babe" you say before gently kissing her forhead and going to the bathroom. "I'll be waiting for you in the living room beauty." and with a wink you desapeared leaving your girlfriend with tons of ideas as to how this would turn out.