Remember how Ruby currently has cute ears and a tail in my quest? Well, Yang has a few scales and a cock. (It's complicated)
The next day, you had an opportunity. Blake and Weiss were both going to be out of the room for a while doing their own things, which meant that you had an opportunity to do something that you've been meaning to do for a long while now. She'd adapted to the changes that Merlot had forced on all of you really well, though her scales were usually covered up by her jacket and she'd taken to wear slightly looser shorts to avoid having a prominent bulge at her crotch. You'd gotten to experience her, uh, 'addition' once before, but that wasn't exactly a situation where you could really focus. Come to think of it, you don't think you've actually even seen what it looks like other than a few quick glances.
Well, today was the time to change that. You and Yang were going to be alone for at least a couple of hours, and you had a growing, gnawing curiosity inside of you. "Hey, Yang?"
Yang looks over from where she's watching something on her phone. "Yeah, Rubes?"
"Do you wanna...you know, do something fun?" There's still a little bit of weirdness if you really stop and think about what you've asked your sister, but any real reluctance on either of your parts was long, long gone. For her part, Yang immediately tossed her scroll aside. "Hell yeah, I've been waiting for you to make a move for ages. I even bought condoms last week just in case this thing actually works."
You smile, skipping over to give Yang a kiss, one that she returns with a passion that leaves plenty of heat inside of you. She starts tugging off your clothes, and you pull off hers at the same time. Your tail swishes slightly as it's freed from under your skirt, and your ears twitch a bit as your shirt goes over them. As you ease Yang's jacket off, your fingers brush over the smooth golden scales that cover her back and shoulders.
You pause, taking a moment to run your hands over them. They meld seamlessly in with the rest of her body, overlapping like little armor plates. Still, they're not hard like a shell, they've got just slightly less give than skin. They're warm, too, just like the rest of her.
Of course, that's not her only new part. You drop to your knees, tugging Yang's shorts and underwear down. Her cock springs free, the head smacking your cheek with enough suddenness to make you let out a little "Eep!"
Yang smiled at your reaction. "Okay, it's not that big."
You scowled at her, wiping the smear of her pre-cum off of your cheek. "I wasn't expecting it to jump at me!" You ignore her barely-suppressed snort of amusement, instead putting your hands under and around her shaft, getting a good feel for it. It wasn't the largest you'd ever seen, that honor went to Red, but it was certainly long and thick enough to leave you seeing stars. You weren't exactly an expert on human penises, but you thought it looked pretty good, too. Kinda...well formed and...robust, maybe? Was that the right word?
There were a nice pair of balls, nestled in a taut pouch at the base of her shaft. You plant a kiss on her tip, cheering internally when her breath hitches and cuts off an oncoming remark. You continue to trail kisses down the side until you reach her orbs, planting a big smooch right on each one. Your tongue trails over them, feeling their warmth. You imagine that you can feel the cum sloshing around around inside of them.
You keep moving your head down and closer, lifting up her balls to get a peek in behind them even as you continue to lavish them with attention. Yang's lady-parts are still there, dribbling and slick from the attention you've shown her, and you slip a finger into her passage as you kiss your way back up her shaft.
Yang doesn't stand still and enjoy this, though. Her hands come down on top of your head, and you excitedly ready yourself for your sister to grab you and pull you down her shaft. She...doesn't do that, though you're certainly not disappointed. After all, she instead puts her hands to use scratching your furry ears, and just like always you absolutely melt at the touch.
To thank her for the attention, you open your mouth as wide as you can, putting your lips around the crown of Yang's length, then do you best to kiss her hips without letting your extra long canines get in the way. You take it slowly, an inch or two every couple of seconds, giving you time to relish the taste of your sister on your tongue and the feeling of her cock spreading your throat. It's even warmer than it was before, and the temperature is rising at a constant slow rate. You knew your sister always burned hot, so you guess she's just heating up more as she gets excited? Mmm...this is going to be your favorite thing on cold days.
It's kinda hard to focus with the delightful assault on your fuzzy appendages going on, and you're pretty sure your tail is wagging happily behind your body, but you do your best to milk Yang's cock with your throat, bobbing your head back and forth as you add a second finger to the one in her passage. Her cock is coming from where her clit used to be, but she still has her g-spot and you focus on that target with everything you've got.
From the loud moan and the way her knees suddenly tremble, you know you've hit the jackpot. "F-fuck, Rubes, I'm gonna burst real soon here..." A wonderfully dirty thought crosses your mind, and you back off of her cock, nuzzling your way down the shaft until you reach her balls. Opening wide, you just barely manage to fit one of them in your mouth, continuing to pump her shaft with one of your hands as you gently suckle and tease her sensitive orb.
Her cock is covering one of your eyes, but you use the other to give her the most wide-eyed, earnest, begging expression that you can muster. It works, and you can feel the orb in your mouth clench repeatedly as it unloads ropes of Yang's hot cum out into the air. The first few land in your hair, but as you lean back more shots of cum splatter over your face, neck, chest, and belly. It's steaming hot, feeling almost like a warm bath as it sits on your skin, and you shudder to imagine just how good it would be inside of you.
Yang lets out a long breath. "God damn, Ruby, that was awesome."
You give her an impish smirk. "Heh, thanks. But now, let's just see how long until you can go another round."
As it turned out, not long at all.