Reader is a faunus.
I made her a cheetah faunus.

So, both Sun and reader share a room in Vacuo. They both knew each other as she had studied in Beacon and met him there.

This is basically being railed by Sun because oml man-🛐

WARNINGS: (inaccurate) mentions of heat, choking, use of his tail, safe sex, size kink, inaccurate sexual descriptions as per usual as my only knowledge comes from our Bio class and actually writing it comes from reading smut on a daily.

I unzipped my vest and stretched as I finally plopped onto the bed. It was currently sunset, and I finally got home. It was so nice to rest on the bed, after an entire day of working my ass off, especially since I was in the early stages of heat. I was lucky it wasn't as bad yet, but it was still there. I still constantly felt...wanting. It didn't matter because I knew it'd get worse after a while.

My ears twitched when I heard the bathroom door swing open and opened an eye to see Sun Wukong, my boyfriend of three months. I smiled and waved lazily at him. He was only clad in a towel that hung low around his waist. My ears twitched, and a million thoughts began racing through my head. Okay, maybe it wasn't my head, maybe it was my body that yearned for him. Sun must've felt something as he stopped, staring at me in shock. "Are...are you in heat?"

I blushed and tried hiding my face in the pillows. I couldn't look at him, as I felt my arousal dampening my underwear. Why did this feel so embarrassing? Why was I suddenly so warm?

I heard an awkward chuckle, "Do you want me to leave the room for a while?"

I lifted my head and turned to see him, nervously rubbing the back of his neck. I sighed. "Honestly, it's up to you. I personally don't want you to leave, but at the same time I do. I want you to leave because this is mortifying, but I don't want you to leave because...yeah. I like having you around. I might enjoy it more now, but...I don't want you uncomfortable."

Sun stared, and honestly, under his gaze, I couldn't help but squirm. My eyes went down to what hid beneath his towel, but I quickly snapped my eyes shut and shook my head. "However, if you were to stay," I began, breathless, as the heat in the room got me hornier for some reason, more desperate for him, "I don't know how much I could control myself. I just think you should know."

Sun stared at the ground, and honestly, the more I stared, the more it ached. Now I see what faunus mean when they see someone hot and they just... it hurts. Even more, somehow.

Holy Grimm.

I stared at Sun, waiting for any movement. He finally took a step forward, getting closer to the bed as I lifted the blanket to hide my face in it. I felt a hand on my head, and I quickly looked up. He looked into my eyes, and his soft, blue eyes made my heart race. He leaned in and kissed me, and it took all of my strength to not let myself lose control and pounce on him then and there, claim him as mine, but I shrugged off the thought. I was never possessive, ironically enough, and yes, I would be jealous, but it was usually Sun who marked me up. Not to mention, we haven't even reached there, yet.

He leaned in closer, a smirk making its way to his face, "I wouldn't mind staying with such a cutie."

He winked and I felt my core throbbing in pain, and I felt my hair stand on end, my faunus ears going back as the fur fluffed up. I stared back, licking my lips, "Please," I whispered, "i don't know what will happen, but I won't... I won't want you to hold back. I want you in me, Sun, but I understand if you don't-mmph."

I felt his lips on mine, cupping my face with one hand and pulling me close with the other. I dropped the blanket and a surge of confidence overcame me, and I settled into his lap, holding him close, grinding myself in his lap. I felt my sense heighten, and his eyes slowly blowing with lust, holding me close as I felt his member poking my inner thigh.

Sun pulled away from the kiss, staring into my eyes, "I'll stay here with you, my beautiful. I'll stay and help you as much as you need."

I kissed him again, only this time, I let my tongue enter his mouth. French kissing him, I grabbed him closer, my nails already going to his hair. Sun let his hands go to the ends of my tank top, lifting it to reveal my bare breasts. He let his lips travel down my lips to my neck, licking, nipping at my skin, and the second he found my sweet spot, and I moaned, he smiled against my skin. He held me closer, his lips slowly going to my bare chest, to one of my breasts, experimentally biting again, which I knew would leave love marks the next day. Finally, he latched onto my nipple, grazing it gently with his teeth, slowly building the courage to suck on it, as his fingers played with my other nipple.

I couldn't help but moan, my core getting wetter as my fingers tangled in his hair. I began grinding on him again, looking for any type of friction.

Sun hummed and did the same treatment to my other breast, and I felt my ears twitch, biting my lip as I wanted so badly to feel him inside me. "S-Sun!"

I felt his fingers ghosting over my skin, finally resting at my hip as he stopped sucking, and placed a gentle kiss on my nipple. He looked up at me, his fingers going to my shorts to untie them, ushering me to get up and slide them down completely. He smirked and licked his lips as as I removed my blue lace underwear. I got back to my place on his lap, wrapping my arms around his neck as he slowly thrusted his hips upwards, emitting moans from us. I felt my core clench on air, and I began begging directly in his ear, letting out moans as I brought my hips to meet his. I felt Sun chuckle. I let myself get on my knees and watched him unwrap his towel, his tail also getting freed as I saw his cock rise. He was thick, that was for sure, perfect length, precum already leaking from the tip, and I couldn't help but nearly drool. He nibbled on the skin of my neck, one hand going to my upper back as the other went to my hips, keeping me close and rubbing me down hard on him. The friction felt good, but not enough, and I saw Sun had some sort of moment of realization. "Y/n," he whispered gently, "do you have condoms?"

I blinked in frustration, "Yeah, in the drawer of the nightstand."

Thank whoever it was up there that he was able to reach it without removing me from his lap. He tore a packet open, rolling it onto his hardened, red cock and pumped himself a few times before finally facing me. "One more time, I'm asking this," Sun said, "Are you completely sure, Y/n?"

I groaned in annoyance, "Yes, Sun, I want you as my first!" I whimpered.

He gently helped me lift my hips, and I sank down on his cock. I'm assuming the fact I was already very soaked, drenched, to be precise, helped him slide in easily, but the stretching feeling was uncomfortable, slightly burning. I whimpered as he grabbed me into a kiss, waiting for me to get used to his size. "You're so tight, Y/n/n. Nngh."

I let my head fall on his shoulder, whimpering as I begged him. "Sun, please, move. Move, please."

He slowly thrusted upwards, hands on my waist as he guided me to a steady pace, and the uncomfortable feeling slowly subsided, and I felt the pleasure. I felt my walls clench around him, my hands on his shoulders as I tried riding him.  It felt so good, so good.

"I can smell your arousal, Y/n," he whispered in my ear, "You make me wanna ruin you."

Still riding his cock, I whispered in his ear, "Then ruin me, Sun. Fuck me until I can't walk."

It must've ticked something inside him, because I felt him quickly lay me on my back, thrusting deeper into me, beginning to thrust at a more brutal pace, looking down my chest as he pressed a hand down my stomach, and only then did I notice. "Can you feel me in your belly, princess?"

I moaned as I saw the bulge, pulling him close, raking my nails down his back as he snapped his hips into mine. I could hear the lewd squelching sound, skin slapping skin, and I heard his quiet grunts, even through my moans. The second I felt him brush a certain spot in me, I cried out. "SUN! Right there, please! Oh my-"

I screamed as I felt him angle his hips to hit that spot again and again. "Sun, more!" I whimpered, wanting more. I felt his hand come down to rub my clit, and I nearly screamed. There was a building pressure in my abdomen, and I moaned as I felt it building up. "S-Sun!"

I felt my walls clench around him, "I can feel you, Y/n. Oh gosh-"

He wrapped his hand around my throat, limiting my air supply, and his tail went to my thigh, gently squeezing. I moaned even louder than I thought was possible, screaming his name like a prayer, feeling the pressure finally snap and dissipate, releasing it onto his cock. I heard him groan in my ear, and when I opened my eyes, I caught him staring.

I closed my eyes for a moment, only to feel Sun pull out and flip me over. I felt exhausted, yet I felt myself yearn for more, even as I was brought to my hands and knees. Sun kissed down my back, entering my soaked cunt once again, rolling his hips against mine. I gasped, my arms starting to give out as he fucked me hard from behind. I cried out, I could feel his balls hitting my ass repeatedly. I felt so tired, but so horny...the problem with heat. Sun's hand returned to my throat, and his tail- harshly squeezing my thigh. His free hand went around my stomach, pulling me back in such a position where he still thrusted in me from behind, but I could still count it as somewhat riding him, if he weren't supporting me with his arm. His tail went in between my legs and ghosted over my clit. My eyes shut tightly as I sobbed. Sun felt my walls clamp around him, and let his tail ghost over my clit again, enough for goosebumps to go over my skin and clench on him even tighter, as he sped his thrusts, hitting that much desire place over and over again.

"Sun," I whimpered, feeling myself get overly sensitive. "Sun I'm close!"

Sun groaned in my ear, his thrusts faltering. "Cum with me, Y/n."

I moaned once again loudly, crying out as he thrusted several more times as I came with him this time.

He finally pulled out, leaving me with an empty feeling as he laid me on the bed, kissing me once again and leaving to throw the condom in the bin. My body was tired, and the symptoms of heat slowly vanished, but they would come again. Luckily, I had Sun.

Speaking of Sun, I felt him climb into my bed, hugging me into his chest, pecking my forehead. I looked up at him, "Would... would you be okay if you helped me with this..?"

He winked at me, "Whenever you need anything, sweetheart, especially when it comes to this, I'll be there and help. Besides," he hummed appreciatively, "I can't wait to see you squirm again, perhaps next time I'll eat you out."

I blushed, "We'll see."

"Oh we definitely will!"

"SUN!" I slapped his chest and he laughed.