WARNING- I have no clue what Ruby's personality is like, so he's pretty much an OC. Also, read at your own risk. 

Dearest (y/n), 

I am writing to you on a matter of utmost importance. I trust your opinion over those of most people I've actually met, so I need you to answer honestly. Does a red dress go better with gold earrings or silver? Also, I'm going to need some help on the shoes. I'm thinking high heels, but I want something understated. The dress will have black embroidery, so I'm thinking black shoes to emphasize this. Please write back with your thoughts immediately. 

Yours truly, Ruby

(y/n) read the letter and giggled. When she'd signed up for a pen pal at the local trainer school, she hadn't thought they'd end up bonding over fashion. As soon as Ruby had learned that she was a girl, he kept wanting her to try on various clothes for him. 

He also needed constant advice on all these little nit-picky details even she wouldn't have thought of. She took a minute to collect her thoughts before writing back. 

Ruby, 

It sounds like an amazing dress. I can't wait to see it! Oh, I forgot to tell you- I'm leaving for Hoenn soon. I'll be starting my pokemon journey there, because my mom's moving to Hoenn as well. I'll bring some earrings I think might go well with the dress. Not sure about the shoes, though. Just sticking with black might be the best choice. See you in three days! I also wrote my new address on the back of this envelope. 

-(y/n)

She walked the letter to the post office, paying for a stamp and handing it over for delivery. (y/n) figured it should reach Ruby in a day or two. 

After she was done packing, (y/n) still had a few days to wait before the move, so she amused herself by reading some of her mom's old books. Wow, she thought, Shautal is really bad. I mean, poetic. Oh who am I kidding, this is garbage!

Her mother walked in just then. "Oh, are you enjoying that book?" she asked. 

"Um. . . yeah. Yeah, it's really, ah, poetic", (y/n) said, just to be polite. 

"I'm glad you think so. Shauntal's an old friend of mine from High School, and she gave me that copy for free. Personally, it's not that good. You can keep it if you'd like."

"No, no, that's fine!" (y/n) hurriedly assured her mom, handing her the book. "You just hang onto it!"

I'm sorry. I had to. Okee, on to the actual story! FYI, that was completely unrelated to the rest of this, so. . . yeah. 

A few days later, (y/n)'s plane bumped roughly on the ground, slowly coming to a stop. She collected her luggage, then ran to her new house, eager to see what it looked like. Her mom would be coming in a couple of weeks, after she finished with the paperwork for selling their old house. She also needed to meet with some perspective clients for her job. 

(y/n) checked the mailbox out of habit, and found a letter addressed to her. She pulled it out, stepping inside her new house and putting her luggage down before opening it. 

It was from Ruby. Apparently, he was coming by to meet her that evening. Strange as it sounded, she'd never actually seen him before, since they only communicated through letters. 

She was somewhat anxious, so she took a shower to help calm herself down, dressing in black leggings and an adorable maroon smock when she finished. Her inner Ruby must've been coming out, because she then pulled her (h/l) (h/c) up into a messy bun on top of her head, picking a gracidea flower from the little garden behind the house to put in her hair. 

(y/n) was lounging around in the living room when she heard a knock on the door. She hurried to open the door. A boy around her age stood there, with raven hair and stunning red eyes. 

"H-hi", she said, suddenly nervous. "I'm (y/n)."

"And I'm Ruby", he greeted her. "It's nice to finally meet you. You're even prettier in real life."

"Um. . . thanks?" (y/n) replied hesitantly. 

"I know you just got here, and this seems kind of weird, but would you mind modeling for me? You don't need to answer right away."

"Okay", (y/n) said. Ruby was acting casually around her, as though he already knew her, even though they were only pen pals. "Um, so do you want to come in?"

"Sure", he replied. (y/n) held the door open so he could enter. 

The two of them ended up on the couch, (y/n) sitting down where she was before. Ruby sat next to her, despite the fact that the couch was pretty long, and there were even a few padded chairs throughout the room. 

"So, (y/n)", Ruby said, "Tell me about yourself. I mean, I know a little from the letters, but not enough to actually know you."

"There's not really much to say. . . I'm used to being alone. Mom was usually off doing her own thing, and Dad works in Johto. I grew up in Unova, and this is the first new region I've been to. Um. . . also, my favorite color is (f/c), and I like (fave desert)."

"So. . . you don't have a boyfriend?"

"What? No, why do you want to know anyway?"

"Then that means. . . you're all mine." Ruby leaned forward, kissing her forehead softly. 

(y/n) froze at the action, startled by Ruby's strait forwardness. "Say, while I've got you here, would you mind trying on a new outfit I designed?" he asked her. 

"I guess so. Where is it?" (y/n) asked. Ruby held up a black lacy bra and matching panties. 

(y/n) flushed a deep scarlet. "You already agreed, remember?" Ruby purred. 

"I didn't know it was going to be lingerie! I thought it would be that dress you were telling me about." 

"Too bad. You said you'd do it. Do you need some encouragement?"

"What do you mean?" (y/n) asked, somewhat fearfully. Ruby slid closer to her, and reached out, slipping her smock up over her head. "Ruby!" she yelped. 

"It'll be fine. . . just relax, (y/n)."

He started to reach for her bra, but she shied away. Ruby pushed her onto her back, pinning her arms with one hand while he took her bra off with the other. 

"See, that wasn't so hard", he said, taking the lace bra and carefully positioning it on her body. He let go of her arms to fasten it on. "We're already halfway done~"

(y/n) gasped when he tugged her leggings down. 

IF I HAVE ANY INNOCENT CINNAMON ROLL READERS THAT DON'T WANT TO BE SCARRED FOR LIFE, DO NOT CONTINUE!!!!!! HELP ME I CAN'T STOP! ABANDON SHIP!!!! Scrap that thing I said about probably not doing lemons. I think OC Ruby runs this ship now. GET OUT WHILE YOU CAN!

Ruby grinned as he saw her wetness. "Well, isn't someone enjoying this. . ."

"That would be you", (y/n) replied. 

He didn't reply, just pulled her panties off instead.

"R-Ruby. . . don't. . . " (y/n) warned. He didn't listen. Instead, he pushed a finger into her opening, causing the (h/c) girl to moan. He didn't stop there, pushing another finger into her. She moaned again, unable to stop herself. 

 Ruby pulled his fingers out of her, taking off his jacket and shirt before he started sucking her breast through the bra. One hand massaged her other breast while his other hand went back to exploring her opening. 

"Ruby", (y/n) sighed. He finally stopped teasing her, pulling his own pants and boxers down. He positioned himself over her, then pushed himself into the girl. 

She cried out, startled by the unfamiliar feeling and the sudden pain. Ruby sealed his lips over hers, silencing her cries. He soon started moving, pulling back and pushing in again. He got faster and faster until (y/n) was screaming for more. 

Ruby pulled out right as they both climaxed. (y/n) stared at him, breathing heavily. 

"And here I though having a pen pal would be boring", Ruby said. He pulled the new panties on (y/n) after licking her clean. She moaned again, but when he was done, she had managed to nod off. 

Ruby smiled down at the beautiful girl beneath him. She was tainted now, his. His forever. 

"My (y/n)", he whispered. "Mine forever."

So this was honestly going to be pretty innocent. I swear, it was! Now Ruby's a semi-yandere, (y/n) had sex, and omg I probably screwed Ruby's character up soooo bad! I didn't read the mangas he was in, so I had to do some research on him, but I still wasn't sure how to write this, so I was just like- ooh, lemon! Then the reasonable part of my brain screamed for mercy from the living hell it was in, and I wrote my first lemon.