You let him decide.

You use the device to tone down Chad's horniness, he is left with a pussy but can think clearly now. You are really curious to see what will happen. Your bully is watching the huge hard dick of your sister and pondering on her proposal.

"We can try it honey, but only if you promise to let me try the other way if things turn back normal. " he tells her. Big burly dude that spend a lot of time in locker rooms and communal showers, his favorite swear word is to call everyone a fag. Now he is willing to take a large dick up his ass, talk about hypocrisy.

"Sure Chad, you will be allowed to put your little winky in my poppy. Now spread your cheeks, I want to try this ass of yours. " she replies.

You really enjoy seeing a total asshole like him being fucked like that, the fact that you will have all of this on video as **** material is an awesome bonus.

"Oh yeah, Chad you're so tight. It's better than your pussy, my big cock barely fits in there. " she screams as she is fucking him. He doesn't reply anything coherent past some squeals, grunts and calls for her to go faster and deeper.

Once the novelty of it wears off you quickly lose interest in this. You could turn them back like they were before but it's funnier to wait a few days before that. Maybe you can figure out a way to make them do humiliating stuff in exchange for a cure.

Right now you have more important things to do.

You just got an awesome idea.