Yang strolled out of her dorm's bathroom, clad in her burnt orange set of lacy underwear, her ample bosom bouncing as she stepped towards her and Blake's bunk, swinging her hips far more than anyone really needed too. Blake was lounging in her black and white yukata, watching Yang with heavy lidded eyes.
"Enjoying the view, Kitten?" Yang asked with a teasing tone.
"How could I not?" Blake asked back. "You ready?"
"Yep," Yang answered, popping her 'p'. "Got your 'magic cock' ready?" Blake answered by opening the lower part of her yukata, revealing a secured black strap on.
"I'm surprised you'd be okay with the scenario."
"I'm down for whatever gets you to fuck me like you mean it," Yang growled with open lust.
"I always mean it, I'm just better at hiding it than you," Blake answered with a smirk as she covered herself back up. "Remember your safe word?"
"Gauntlet. Not like I'll need it. This thing can't be that strong, Weiss said it only worked for an hour tops," Yang said confidently, sitting at the end of Blake's bed. "Looks like we're ready to get in character." Blake nodded, cleared her throat and started the timer sitting on the bookshelves next to the bed, the agreed upon sign that they had started.
"So, Blondie, why do you need Kat's services? You're not exactly lacking up top," Blake commented in a sultry tone.
"I know, and call me greedy, but it's just not enough for me. I need them bigger," Yang said, almost begging in a higher pitched voice than her normal voice. "You can help, right?"
"Of course. Climb on Kat's magic cock and I will solve that problem in no time," Blake answered, opening her yukata and exposing her strap on and pert breasts to Yang, "If you can handle it, of course."
"Thank you so much, Kat." Yang crawled over to Blake until she had her hips over Blake's. "Do I just, y'know…"
"I can do it for you," Blake finished. She slid Yang's damp panties to the side and slid her black cock into Yang's dripping pussy. Yang let out a gasp.
"Oh wow, it feels so good."
"It's my magic cock for more than one reason." Blake put one long, hard thrust into Yang just to watch her bosom bounce. "Don't be afraid to give me a hand here, Blondie." Blake began to set her thrusts into a slow, constant rhythm.
"O-of course," Yang replied. She brought her hand down and began slowly started circling her engorged, throbbing clit. She threw her head back and let a loud, high pitched moan loose.
"You're right, you needed this badly," Blake teased, picking up the pace with her thrusts. All Yang could do was nod and thrust herself on to Blake's fake member, forcing herself closer and closer to the edge. Before long, she let out a shuddering moan and her whole body bucked, forcing her breasts forward. Blake faked her own orgasmic moans and spasms, keeping her eyes open to keep an eye on Yang. As Yang came, her breasts puffed out in short bursts timed with the waves of ecstasy. As Yang's orgasm came to an end, she caught her breath and looked down at her newly improved bust. Her bra was still holding her expanded breasts, but they were spilling out over the top and out the sides, and Yang could tell that the bra's seams would give out pretty soon. Yang faked a shocked gasp.
"Oh my gosh Kat, they're great."
"It's my job." Blake gave Yang a devilish smirk. "So, you ready for round 2?"
"R-round 2?" Yang asked with false confusion. "But I'm already done."
"You payed for a twenty-minute session, Blondie." Blake sat up and looked Yang in the eyes. "And it would just be cruel for you to miss out on all that time together."
"B-but they'll be way too big by then," Yang replied in a panicky tone.
"Will they?" Blake asked with a raised eyebrow. "Don't you want to burst out of that bra?" Blake slowly pushed Yang down onto the bed and put herself on top of her. "Won't you enjoy the looks people give you with your amazing new tits?" Blake thrust hard into Yang, forcing a moan from Yang. "Don't you want more of my magic cock?" Blake rolled her hips and put a few quick thrusts into Yang, jiggling her breasts.
"Oh god, yes!" Yang cried out, before covering her mouth. "W-why did I say that?"
"You want to give in to me, of course," Blake growled into Yang's ear as she began her constant thrusts. "You want massive fucking tits. You want me to fuck your brains out. You. Want. Me."
"I-I need you!" Yang exclaimed, bringing Blake closer. "Make me as big as you can. I need it now!" That pleading appeared to set Blake off, throwing off her rhythm as she began to thrust powerfully into Yang's now sensitive pussy. Yang buried her face in the crook of Blake's neck and let out a muffled moan before going slack from her second orgasm. Blake slowed down and held herself up so she could admire her handiwork. After a few waves of orgasm-powered breast growth, Yang's bra snapped and her breasts burst forth, growing to what Blake guessed was around a K cup. Blake tossed the ruined bra aside and stopped her thrusts.
"Roll over," Blake commanded.
"A-anything you say, Kat," Yang breathily answered. She turned over and rest her weight on her bra bursting bosom. Blake removed her yukata fully and tore off Yang's soaked panties, tossing it by the equally ruined bra. She got a firm grip on Yang's hips and thrust as hard and as fast into Yang as she could. It took barely any time to send Yang screaming into another orgasm, puffing her buxom bosom to the size of watermelons and lifting her further up. All through that orgasm Blake had kept aggressively thrusting, making it Yang's strongest one yet and the best for her breast growth.
"How big do you want your tits now?" Blake growled.
"I don't care!" a shaky Yang cried out, "Just don't stop!"
"That's more like it." Blake hauled Yang up off the bed and on to her lap, while continuing the endless thrusting from behind, forcing Yang's impressive bosom to bounce and jiggle like jelly. Blake squeezed both of Yang's massive breasts roughly, making Yang shriek out a moan as she hit yet another orgasm. Her breasts forced their way around Blake's tight grip, spilling out of the hand-bra Blake had provided and resting on her lap.
Mercifully, the alarm went off and Blake ceased her thrusts and let Yang's boobs drop, hanging down to her navel like teardrops from Yang's chest. Yang leant on the bed to keep her balance, now thrown off by the massive increase in weight, and catch her breath.
"You're looking much better, Blondie," Blake whispered in Yang's ear as she reached around and tweaked Yang's nipples.
"Uh, g-gauntlet, sorry," Yang nervously replied. Blake took her hands off of Yang and put them up defensively as she pulled away.
"You don't have to apologise. Did I do something wrong?" Yang turned to face Blake, cupping Blake's face with a hand. She softly locked lips with her raven haired partner, before finishing with a peck on the cheek.
"Not at all. I just want us to enjoy these without the whole roleplay thing going on," Yang answered softly, holding up her massive mammaries with her free arm. "You can keep playing with them if you want, just as Blake instead of Kat. Might get some better dialogue that way." Blake rolled her eyes as she gingerly took hold of Yang's bosom, slowly burying her face in Yang's increased cleavage, planting quick, soft, little kisses on the inside of Yang's expanded breasts. Yang hummed contently. "As fun as roleplay and rough sex is, I can't help but love when you do that."
"Well, thanks for humouring me," Blake replied into Yang's muffling chest.
"Any time, babe," Yang breathed. "Want me to eat you out?" Blake immediately stopped kissing Yang's cleavage and looked at her with needy eyes.
"Thank you," Blake answered desperately. Yang lay down and rolled over, putting her face under Blake's dripping pussy and catching the drops of Blake's juices in her mouth. Blake carefully lowered herself onto Yang's face and took in a big gasp as Yang's tongue went to work, massaging Blake's most sensitive places. Blake gently massaged Yang's breasts in return as Yang slowly pushed her closer to an orgasm and groped and squeezed her ample rear. The excitement from earlier, in addition to Yang's skilled tongue, had Blake purring with pleasure in no time. Soon, she locked up as her whole body tensed in orgasm, her orgasmic moans muffled by her locked mouth. As the waves of pleasure, as well as Yang's tongue, slowed down, Blake loosened up, almost slumping down on top of Yang, her quick reflexes keeping her almost upright. She shuffled off of Yang's face and lay next to her, resting her head on one of Yang's massive breasts.
"Enjoying my pillows, Blakey?" Yang giggled.
"Best pillows I've ever had," Blake drowsily replied as she flashed a dopey grin at Yang. "Do you think we've got time for a nap?"
"Probably. Ruby and Weiss are probably out for the day." Yang wrapped an arm around Blake and snuggled close to her now snoring partner. Before long, Yang had joined her partner in post-coital slumber, beaming grin still on her face as the orgasmic glow faded away ever so slowly.