This is the fourth and final (for now at least) part of 'Helping out girlfriend's sister' series. This is a direct continuation from part 3, unlike the others. So if you want to follow what's going on in the story, you might want to read that part first.
....
"So...?" asked my girlfriend, Jen. She was standing naked in the doorway, her silk nightie now a puddle by her feet as she had slipped it off seconds earlier. She was staring at her sister, Jess. Who, unlike Jen, was still wearing her masseuse uniform (although, rather bunched up around her waist now).
She was lying on the massage table across from me - with a double ended dildo halfway up her wet, glistening pussy. The other half was in my ass, giving me the most pleasurable and painful experience of my life. She started to slowly grind into me again, staring back at my girlfriend. Both of them ignored me.
"So...?" replied Jess. She slowly raised her hand and wrapped her fingers round my throbbing cock. As if daring my girlfriend to stop her. The cock ring that was tight around it had turned it into a solid rod. My balls were painful orbs that bounced with each movement and the slick sound of oil and pre cum filled the silence as she began to slowly jerk me off again, in rhythm with her thrusting. Neither of them broke eye contact.
Jen stood her ground and bit her lip. Then, with her eyes locked on her sister's, she moved her hand to her pussy. Her fingers brushed lightly against her trimmed bush. "You do know you're playing with my cock, right?"
Jess thrusted a little harder. I winced as the dildo shot up further into my ass.
"You've always hated sharing," she replied. She grabbed my cock harder and slipped her hand up and down. She then broke eye contact and looked at my cock her hand. "Anyway, you've not been playing with him right, from what I've heard. These balls need to be emptied." She gave them a squeeze, as if to demonstrate. I squeaked in responce.
Jen, still stood in the doorway, parted her pussy lips to reveal her clit. With a shallow breath, she started to gently rub it. From here, I could see she was already wet. It was like I was in some weird twilight zone. Both women seemingly having a normal conversation while ignoring the fact that I was naked, hard and being used like a sex toy.
"And I've built up all this cum in these balls," continued her sister, as she lay with me. "So I get to enjoy the results.".
Jen continued to finger her sensitive bud as she now looked at my engorged cock in her sister's hand. Her eyes widened with every stroke of her fingers. She strummed herself in time with each jerk of my rod.
"Jen, I'm so sorry. I didn't..." I started to say.
"Shush," she replied, removing her hand and slowly walking over to the table. Jess was working me harder now. My orgasm prevented from exploding in her hand because of the cock ring. My balls felt like they were the size of space hoppers.
Jen stood beside me. My girlfriend. The woman I was meant to be devoted to. But who I'd ultimately been betraying with these sordid massage sessions. Even though, as I kept telling myself, I wasn't entirely in control of any of those sessions. She looked down at my cock, her eyes following her sister's hand as it worked up and down my wet stiffness.
"Have you two fucked yet?" she asked.
"Err," I started to reply. Lying now seemed a waste of time as we were already down the rabbit hole, so the speak. But I still didn't want to say anything to make things worse.
Although, how much worse could they realistically get? Her sister gave me a huge thrust, gasping as the dildo went completely inside her. Her pussy lips were now basically grinding my asshole, we were both so full.
"Now come on, don't lie," she teased, as her hips swayed and wriggled against me. She looked at my girlfriend.
"Does this count? Because if so, three times." she said, with a wicked grin. "If not..." she trailed off, as she squeezed my cock again.
Jen was still staring at my cock. A small smile then crept along her face.
"And how often with the ass fucking?" she asked, watching her sister thrust the dildo in and out. "I mean, I know you like a bit of ass play. But we've never gone this far. I'm a little jealous."
The sound of slick, wet thrusting and jerking was all that could be heard in response to her question. I wasn't sure what to say. Jess thrusted again, to get me to answer.
"This is. The first. Time." said Jess, with a thrust on each sentence. It felt like the whole dildo was going to slide out of her pussy and end up in my ass.
"And the cock ring?" asked Jen, marvelling at the tight rubber rings around my cock and my balls. "You've never worn one with me before."
"Well, I didn't want him to bust so quickly, seeing as you already got him most of the way there this morning," grunted Jen, thrusting her hips and penetrating my ass more. Her tits jiggled with each movement. "He'd be useless if this thing went limp after two minutes."
She let go off my cock, and grabbed the sides of the table as she sped up her thrusting. Her thighs squeezed me either side as she gripped me harder.
Jen giggled. She continued to stand there, staring at my cock as it bobbed up and down with the movements. A little bit of pre cum flew off and landed on her stomach.
"Well, we might have something to stop that," she said, wiping my cum off with her finger. She licked it and wandered off to her bedside table. Bending over, her ass and pussy was on full display. I got an eyeful of her glorious pose and couldn't stop staring. I loved it when she bent over like that. And she knew it.
A kick in my ribs brought me back round.
"Excuse me," said Jess, looking at me slightly annoyed that I'd momentarily forgot where I was.
"Don't be jealous, sis," laughed Jen, as she stood up and waved a box of pills at us.
Oh no.
"Is that...?" started Jess, a mischievous grin on her face. She stopped thrusting to try and get a proper look.
"Yep," replied Jen. "We bought some a while back for a naughty weekend away. Do you remember Dan?"
