An unexpected scene....(a)

The scene that greets you doesn't quite register at first.
"Careless Whisper" is playing softly on a bluetooth speaker, and the scent of perfume is heavy in the air. Jenna is lying on the guest bed, dress bunched around her waist. And her sister, Karen, has her face buried in Jenna's cunt.
"Mmm.... it's been so lonnnng.... you still know what to do..." Jenna's voice is dreamy and sensual, and her breath is coming in shudders.
"You taste just like I remember, Jen." Karen is expertly working the snatch with fingers and tongue.
"Oh... look who decided to crash our party, sis." Jenna eyes you smugly, and Karen stops to regard you with lidded eyes.
"What... the ... fuck... is going on in here?" You are dumbfounded at the scene of lesbian **** in front of you.
"Well, James. Since you decided not to be here when we got back, we decided to have some fun, like in the old days... before you knocked me up..." the contempt in her voice hurts, but you can't deny your arousal at the taboo act being performed.
"We used to do this all the time, Jameson..." Karen laughs. "She never told you?"
"Of course not!" Jenna laughs.
"Jenna this is... this is wrong on several levels." You can't tear your eyes away, though.
"Really? Your little soldier down there doesn't seem to agree with you. Are you getting excited for me, or my sister?"
Karen resumes her cunnilingus, and Jenna moans as she crooks a finger at you. "Come on, James. Take it out! Jerk off while you watch Karen work. Maybe you could get some pointers."
You reluctantly obey. "But...you always said I was good at it..."
Jenna laughs. "Good for a man, but how.... mmmmf.... could you possibly compare to this goddess? Who knows you better than your big sister?" She grabs Karen's head, pulling her in and arching her back in pleasure. "Either stay and stroke or get your ass to the couch, James. Your choice."
You spit on your palm and start stroking. The scene is hot after all, despite Jenna's uncharacteristic cruelty. You knew she was pissed at you, but this is on another level.
"Come closer! I can't see you jerking it all the way over there..."
You move around to the bedside. Karen pokes her head up.
"You always said he was huge, Jenna. I mean... he's big, and thick, too, but not like... porno big or anything." She looks a little disappointed, but then shrugs. "Bigger than Jack anyway."
Your emotions are quite confused. Clearly the girls are venting some aggravation towards you right now. **** is probably a factor, too.
"Yeshh.... Karen..." Jenna wraps her legs around Karen's head, and writhes in pleasure. "ooh...OOOhhh... right there..."
You stroke faster and faster as Jenna's moans grow higher and higher.
"I need your pussy, get it up here..."
Karen obliges, catskinning her dress and swinging her hips up to Jenna's face as she continues to work her snatch while inverted. Karen's body is exceptional despite some chubbier bits than Jenna.
"Ooh, Jenna I think he likes me..." Karen laughs, and begins moaning as Jenna works her tongue into that crimson crowned pussy.
"Yeah, James? My sister's body gets you hot, doesn't it? Are you thinking of all the nasty things you could do to it?"
You say nothing.
"Answer me, James! Tell me the truth, or get out now..."
"...yes." You stroke harder.
"Oh, I knew it! Your husband wants me, Jenna! Should he get what he wants?"
"No way!" Jenna locks her legs around Karen's head, causing her to squeal. "I'm keeping you to myself. He's pissed me off so much today, he's lucky I'm letting him watch."
"Jenna... I'm sorry..." you are, you realize. This is hot and humiliating and cruel, and you regret whatever you did to make her do this, but you also want to say whatever it takes for her to let you do anything besides jerk off.
"Oh... should we give him some relief, Karen? He does look sincere..." Karen rolls off, and smiles.
"Sure! We're magnanimous ladies. Come here, Jameson."
You end up on your back, with the sisters stroking your cock while they make out with each other. Often, they get caught up and stop stroking, only to laugh and resume. Every time they start to build a rhythm, Jenna smacks your balls hard, bringing a grunt of pain.
Eventually, the **** is unbearable....
"Please...."
"What's that baby? You want to cum?"
"Yes, please..." Jenna shakes her head.
"Is that how you ask?" Karen takes your cock in her mouth, and you nearly scream at the pleasure of it. Jenna grabs her sister's hair, pulling her off.
"He hasn't apologized properly, or asked properly yet. Don't give him what he wants." She kisses Karen, stroking you furiously until you think you're about to pop, then backing off.
"Please! I'm very sorry for pissing you off today! I won't do it again, please! Please let me cum!" You'll do anything they want in this moment, you realize.