Young wife gave me her bottom as penance

My wife and I were separated for a few months as she considered divorce. She went back to her home state. I followed a few months later.
She had changed her mind and was somewhat contrite.....and started to have sex with me. Then she stopped and admitted that she'd cheated on me and had sex with a few guys while we were apart - but that "I've never let anyone in my butt - I'd like to offer it to you now. You'd be my first." I guess this was supposed to be a peace offering, or some such....
We were on the fold-out couch in the apt she shared with another girl.
She was naked and got up to bring us some wine to help us into this new experience.
Unbeknownst to me - her roommate's boyfriend and his bud were sitting down the hall in the kitchen, when she walked in to get the wine from the fridge.
Apparently the girls were used to walking about in their panties when guys were over, while getting ready for bed or work. AND - one day when my wife was running the vacuum in her T and panties her roommate's boyfriend watched her from his chair - then got up and told her again what a great little ass she had, stuck his hand in her panties, felt her up - getting her horny - until they had sex on the floor.
But naked - was new. But still OK I guess. She just said "hi!" and told them to be quiet as she walked out - giving them a nice look at her bush, teats and "great" little young butt.
We had a big glass of wine, then she got me as wet as she could with her mouth. She straddled me and began to ease herself down on my dick. I am not hugely long but I am pretty thick, with a big crown on my tip. She was having some difficulty getting my head into her tight little pink butt hole. She started out giggling at the novelty of it all - then she began to moan softly - and gave a little girl grunt as my head popped through and into her. I asked how she was doing - and if she wanted to stop. She said "No, I've sucked and fucked too many guys while we were apart - yeah it hurts but I want to give this only to you!"...as she slid slowly down to sit on my balls.
My young wife has a very tight pussy - but of course it's nothing like her tight little virgin bottom.
I remember it feeling like I was sliding into a tight ring of flesh - sort of like a girl wrapping her thumb and just one finger tightly around my dick to make me cum. I came quickly while we kissed so passionately - me moaning and grunting into her mouth - her doing the same but for very different reasons! The idea of it working on both of us ~!
It hurt her. No two ways.
We lay in each others arms afterwards. I didn't apologize. But I wasn't happy to have hurt her. It was her idea - and her attempt to patch things up.
I should mention that as she was sliding down on my dick I looked over and saw her two friends from the kitchen had come into the room ...spectating her whole experience. It was only a little dark from the street lights outside - but I could tell they were both jacking off as they watched this cute friend of theirs giving up her butt to me. I tried to wave them away - but no way were these jerks going to miss this show, with my very visible naked wife riding atop of me and making these sexy female noises!
I came loudly in her - just to irritate these guys - as all they could do was squirt on the carpet!
I have to say - this was the only time we've used her butt hole with my dick. I know other guys like it - and have read that even women get off on it. (maybe - unless that's some guy writing)
Neither of us much liked it.
I much prefer her tightly clinging cunt. Although, she gets really horny when I lick her butt hole after pouring beer between her cheeks, and does have mighty orgasms when I slip a finger tip into her butt while we're fucking - but that's just a sensation - a far cry & nothing like a fully hardened dick pushing its way into her. She even cums when I make myself cum by sliding between her butt cheeks - to squirt on her back, while she fingers herself beneath us.

I never told her about the audience which she'd had. She'd punished herself enough that night.