Butt of course

"Well now you've gotten me all worked up." Emily was grinning down at him as her cock began rise again. Alex moved to lower his mouth but sh stopped him. "Ah ah ah. Assume the position, I'll teach you to make your big sister worked up." Alex was giddy with excitement as he hopped up and bent over the couch arm. Emily was still sitting down as a total coincidence put his mouth right against her cock. He gave it a few licks as Emily laughed at how cute he was being. "Seriously little sis, it's like you've never tasted my cock before."

She patted the back of his head as she got up and walked around him. She started to play with the plug in his butt. Feeling it wriggle around inside him wasn't as much as fun as he was anticipating he was about to have so his moan was kept to the involuntary. She got bored when he wasn't being his normal vocal self so she pulled the plug out. She moved her cock still dripping with his spit up and down over his tight little femboy hole a few times, applying just enough pressure for him to feel it without pushing inside. She did this over and over as Alex tried to resist pushing back. He knew she was teasing him and that she liked doing it.

Finally he cracked. "Please big sis fuck me with that huge cock." Emily slapped his ass and pushed slowly but surely. The pressure built until she finally popped inside. The feeling of being filled again was the second best thing he could imagine, right after making Emily happy.

"Fuck were you always this tight." Emily moaned loudly as she slowly but surely worked her cock inside him. This being her first time, even if she didn't know it, was making it way more intense. When she was all they way inside she stayed there. Alex was loving the feeling of fullness and he could even feel her heart beat in her cock as it pulsed inside him.
"Fuck I could wear you as a cock sleeve all day." Emily grunted in his ear as she pushed her already bottomed out cock further. With Alex on the couch arm he felt his butt being squeezed by her hips as she tried to get even more of her cock inside him.

Alex did all he could think of. He dropped his hands and feel face first onto the couch and pulled his cheeks apart to give her those precious extra centimeters. Emily filled him as soon as he did and the two stayed like that for some time, enjoying the warmth and comfort the other was providing.

It ended eventually as Emily's entirely new hormone system decided that the cutesy shit was all, admittedly a lot of fun, but there was boy hole not currently being fuck and why was that? Her hips pulled back achingly slowly as her cock dragged itself out of Alex. He felt empty as she pulled out but the feeling was belied by her cock rubbing against his prostate the whole time.

"Ooooohhhh fuccccckkkk." Alex arched his back and moved to drive her cock more against his g-spot. Emily was in her own world of pleasure as Alex's ass tried to pull her back inside the entire time she pulled. Once only her crown was inside she pushed forwards slowly.

Because Alex had been angling his body when Emily thrust her head rammed against his prostate. He fell forwards as he came from that alone. Emily didn't notice beyond that of a feeling of even tighter boy hole.

She got into the fucking, slowly speeding up until she could no longer go any faster. She hit his hips with a quiet smacking sound. Alex began to push back against her as she fucked him and together they worked her cock the way only a true born cock slut femboy and his futa big sis could.

"Fuck Alex you're ass is ssssoooo gooddd." Emily muttered, her hands gripping his hips tighter and tighter as the feeling of tension built in her once again. "Fuck I'm going to cum little sis, I'm going to in your slutty little ass."

"Yes please big sis, cum in my butt, I love feeling you fucking my ass. Please fill me up with. Please." The begging came from a deep place inside him, a place Emily's mark had implanted.

"FUUUUUCCCCK!" Emily roared slamming her hips into him once more, shoving him into the arm rest painfully as she flood him with her cum. She came so much Alex could feel the amount pumping into him. It was so long he was sure that when he stood up he would have a bulge.

Emily pulled out of him and leaned down to kiss his butt. "Mmmmm, good girl." She patted his butt and he felt something cool push against him. With his butt plug back in place Emily walked around and collapsed onto the couch. "Fuck was you ass always that amazing?" She looked genuinely stunned by this experience. Alex looked up from his place waiting for feeling to come back to his legs. "Ahh you are so cute." She lifted his upper body up and climbed under him, resting his face on her soften cock. He began to suckle it because it felt right. He did not that her cock didn't taste like it had just been in his butt it tasted really nice, and not just her previous heavenly dick taste.

The moment was disturbed by the sounds of a phone pinging. Emily groaned and lifted Alex off her cock. He wasn't surprised, this close to uni they shouldn't ignore this sort of thing.

Alex felt feeling coming back and moved to sit on the couch.

"YEEEESSSS!" Emily's sudden shout made him jump a little. She came rushing into the room holding her phone like a holy relic. She was grinning from ear to ear and it made him grin as well.