Thanks for the interesting request Space_Walrus23! I hope this is along the lines of what you were looking for~

Katakuri X Vinsmoke Reader

Keep your mouth shut. Just keep. Your. Mouth. Shut.

You reminded yourself to stay quiet while your jaw and fists clenched in anger.

"What, not going to deny it (Y/n)?" Your brother, Ichiji snickered. "Then you know it's true. You're almost as worthless as Sanji. In fact, it would've been you we would've given up to the Charlottes if it wasn't for his existance."

Your sister, Reiju stared at you blankly while the remainder of your brothers and father didn't even acknowledge your presence. The look your sister gave you would've come across as hurtful if it wasn't for the fact that you knew she wasn't keen on how the the rest of the family treated you and Sanji. The only reason she didn't seem more sympathetic was to avoid father's wrath. You understood that. She was stronger than you and couldn't afford to fall out of his grace.

That being said, her blank stare was her way of telling you to stay calm and let it blow over. Your brother would get tired of antagonizing you. Eventually.

He continued to go on, listing everything he decided made you worthless to the family as you allowed yourself to get lost in thought and take in your surroundings.

Your brother Sanji had disappeared when you were all just kids. And now, years later, he was set to be married to one of the younger girls in the Charlotte family. The marriage would create an alliance that would benefit everyone involved and your father wasn't about to pass that up. He wasn't willing to sacrifice one of his best children though. No, the options were you and Sanji and the only reason you weren't picked was because you came out somewhat stronger than him.

As you checked around the room you were all seated in, noting the pastel color palette, the perfectly white furniture, and the distinct absence of other people, you allowed yourself to think about your unhappy childhood. Ichiji wouldn't notice you zoning out. Not for a while at least.

All of you were made to be strong, stronger than any normal person. The only problem was, Sanji never developed his strengths like the rest of you did. Though you say that loosely. He was considered a failure but so were you, just not to the same degree. You struggled to keep up with your siblings. While they improved in leaps and bounds, you worked overtime to stay half as tough as them. That did nothing but make you a disappointment. And while the teasing was bad as a small child, it only got worse when Sanji disappeared. With him no longer there to take the brunt of the family's aggression, you took on even worse torment.

To this day it hadn't stopped. Reiju was your only saving grace. When it was only the two of you, she was kind. If you needed to cry, she always had a shoulder to lean on and she always encouraged you, promising things would change someday. You weren't so sure about that but you let her say it anyway. It gave you some form of hope.

"Hey! (Y/n) are you even listening to me?" Ichiji slammed a fist on the table in annoyance.

"Relax." Niji rolled his eyes. "She's too useless to even pay attention."

All three of the brothers laughed at that.

"What a waste of space." Yonji added.

Reiju's stare became more intense as she saw the anger flash back to life in your eyes. But you'd been polite long enough, you weren't up for dealing with it anymore. With that in mind, you suddenly stood up, almost knocking your chair down in the process.

"I'm going out for some fresh air." You said through grit teeth.

"Do yourself a favor and refrain from making a fool of yourself while you're gone." Your father said spitefully.

"Yessir." You nodded and left the room quickly.

The tension didn't begin to leave your body until you were out of the room and halfway down to the first floor of the gigantic Charlotte mansion. The halls were huge and took time to navigate but your anger made you walk fast and with a purpose. You needed to get as far as you could from your family, even if it was only for a few hours. That was all you needed to regain your composure and be able to tolerate being around them again.

You let out a sigh as you turned a corner, ready to head down yet another flight of stairs, only to almost fall on your ass as you stopped to avoid running into someone. It took craning your neck some to be able to look up far enough to see their face. And that wasn't all that helpful since half of it was covered by a thick scarf. But you were able to see a pair of sharp, crimson eyes. His hair was about the same color and cropped close to his head. And the man was completely clad in leather. Tight pants and a vest a bit to small to close around his imposing chest. It was like he never grew out of a goth phase but it still somehow looked good on him. In fact, the man was gorgeous.

"I-I'm sorry, I didn't see you there." You silently cursed yourself for stuttering.

You'd seen his wanted poster once before. This was Charlotte Katakuri, your soon to be brother in law. Ogling him probably wasn't a good idea. With that in mind, you sidestepped to walk around him and continue on your way, only to step back instead as he moved back in your way.

"You're one of the Vinsmokes." He stated, his deep voice making your heart skip a beat.

Did you develop the hots for the man you'd only just met? Your hormones needed to calm down.

"Yeah, Vinsmoke (Y/n)."

He squinted down at you suspiciously for a moment. "What are you doing wandering alone?"

As far as you knew, you were allowed free range of the halls and some select rooms. The question threw you off.

"I thought I'd go out for some fresh air is all."

He looked over your shoulder, like he was looking for someone else before focusing back on you. "By yourself?"

"Yes?" He seemed caught up on it just being you. "Is that a problem?"

"...No."

With that, you managed to step around him and continue towards the stairs.

"But I haven't seen your family separate. You've stayed close together since you'd arrived."

He was right about that. Your father liked you all staying close together in such a new environment, surrounded by people that weren't quite in an actual alliance of any sort with you.

"I needed some time away from them." You answered, turning a bit to see he had twisted around to face you again.

He nodded like he knew exactly where you were coming from. "Care for some company?"

"Um, sure, I don't see why not." Your heart picked back up as he walked by you.

It was crazy to develop a crush on someone like this and you told yourself it was his looks that were making you feel so off. He was extremely handsome and it made sense to be attracted to a good looking person. Everyone feels something like that from time to time, it was normal. You were able to relax a bit as you convinced yourself it was no big deal, but you'd missed something Katakuri had said in the process.

"Did you hear me?" He grumbled.

"Oh, sorry, I was thinking. What was that?" You blushed lightly, embarrassed that he had to repeat himself.

"What made you need to leave your family for a bit? It seemed like you all got along fine."

"Well...." It wouldn't hurt to confide in him a bit. Sometimes all you need is a stranger to listen to your problems. "they all get along with each other. Let's just say I'm the black sheep of the family and they don't like me."

"Even your father?"

"He tolerates me." You admitted. "But that's about it. They get to be a bit much to handle at times and right now happens to be one of those times."

He hummed in acknowledgement of what you'd said as you hit the huge front doors of the mansion. He opened one for the two of you with ease, letting you go through first. When it closed behind him and both of you had continued walking, now on the path leading into town, he spoke up again.

"Do you hate them?"

Katakuri was asking a lot of personal questions. Ones that should have had you on edge, but you didn't care at the moment. It was a nice change of pace having someone besides your sister willing to listen to your problems.

"I think I do but I feel like it's something I shouldn't say. They're family after all."

"They don't sound like a real family."

"Like yours?"

He glanced down at you, holding your gaze for a bit before looking back towards the trail. "Like mine."

"Well yours must be nice then." You sighed. "I'd like to say it'll be nice getting to see them all since Sanji's marrying your sister, but I doubt my father will have the rest of us stick around."

Katakuri tensed up at that. "That's a shame."

That gave you butterflies. It was like he was actually liking you as a person and was hoping to see more of you in the future. That'd be nice if that was the case.

"Not really. You wouldn't want to deal with my siblings anyway. They're about as pleasant as getting your teeth knocked out."

He gave a soft chuckle. "You aren't like them."

"You think?" You couldn't help but smile up at him. Handsome and sweet. Your heart wouldn't settle after hearing that.

The two of you wandered around the mansion for a bit, exchanging small talk until he had to go back. It was a shame seeing him go, you were really enjoying his company. But you were probably due back to your own family as well. As much as you'd rather not deal with them, Katakuri had put you in a good enough mood that you knew you could put up with them for the rest of the day.

----

It was still nice when evening came around and your family split into two groups. You and Reiju were sharing a room while your brothers shared another and your father had his own. All the men in your family decided to stay together for a night of drinking as they were offered copious amounts of alcohol by Big Mom. They even had plenty of beautiful, busty barmaids to keep them company. When all that showed up, you and Reiju took that as your cue to retire to your room.

Before that though, you'd gone to see Sanji and had a short talk with him. Understandably, he wasn't happy with the arrangement and you sympathized with him. You and your brother were never close, but there was no hard feelings between the two of you. So you kept the meeting friendly without getting too cozy. It wouldn't be smart to be getting on his good side and risking your father knowing. You weren't considered as useful as your other brothers and sister but he still wouldn't like you getting along with the child he considered to be his worst failure. It'd only make things worse for you.

Not long after you had left him and made yourself comfortable for the night with Reiju, she decided she needed to go for a bit of a walk before heading to bed. She had a habit of getting restless from time to time so you weren't all that surprised. Plus having the room to yourself for a bit was enticing. It'd be the last bit of quiet you'd get for a while with the wedding happening in the morning.

You took full advantage of the alone time, reading and enjoying not being heckled by your brothers. Reiju was taking longer than you expected to come back but you assumed being around the Charlottes just had her on edge and she was working off her nerves. With that in mind, you called it a night after a couple hours and settled in to bed.

The second you had burrowed under the covers, there was a knock at the door that made you groan. If it was your brothers looking to get their kicks by keeping you up all night, you were going to slam the door in their faces. You threw off the sheets and opened up with a scowl.

"If you guys are hoping to antagonize me you have...."

Katakuri stood in the hall with an eyebrow raised and you felt the nervous butterflies start up again.

"I'm so sorry, I thought my brothers were here!"

"No, just me."

"Was there....something you needed?"

His eyes flicked to either side of him, like he was checking the halls while trying to not be suspicious. "Can I come in?"

"Sure, I guess." You stepped back, making room for him to duck under the doorframe and straighted out in your temporary room.

There was a small sitting area off to the side of the beds for you and your sister. Katakuri and you made yourself comfortable there, him in the only couch as the armchairs weren't big enough for him.

"So what brings you here so late at night?" That should have been the first thing you asked him but the shock of seeing such an important member of the Charlotte family at your door kept you from formulating the right questions. Not to mention he was a Charlotte you had developed some kind of affections for.

"Your brother is marrying my sister tomorrow." He folded his arms over his broad chest.

"Yes, that's been established."

"How much do you care for that brother?"

"Um, I'm kind of indifferent about him. Why does this matter?"

"If something were to happen to him and the rest of your family, would it bother you?" He ignored your question and sent another your way instead.

"What do you mean something? This isn't making any sense."

He shook his head and leaned forward until he was level with you. "You told me you don't get along with your family, that they hate you and the feelings are mutual. What if I told you there was a way to get away from them?"

"I'd ask you why you care so much. You don't know me."

He paused for a heartbeat, eyes fliting around the room like there was something nagging at him. When his crimson gaze landed back on you, you had to fight to remember how to breath. He was, quite literally in this sense, breathtaking.

"I can offer you an out but in return, I'd like to explore the possibility of some kind of relationship between us."

"I don't know if I understand what you mean by that." You frowned but you almost shook with excitement. A way to leave your family behind and get a chance to see if this was more than just a quick crush. That'd be a life changing opportunity indeed.

"You feel it too, I can tell."

"Katakuri, you aren't making sense."

He huffed, dragging a hand through his hair. "It's difficult to explain, but I think I feel something for you, and I think it's worth looking in to."

Your mouth opened slightly as you let out a small, surprised noise. It was mutual then. and here you thought love at first sight was an idea that belonged in story books and fairy tales. 

"So you think we should....get together?"

"Yes. But whether or not we try to is based on you. I need you to answer me truthfully. Do you care what happens to your family?"

It wasn't hard to tell what he was hinting at. Tomorrow wasn't going to go like you thought it would, like anyone in your family did. If things were supposed to go south and something terrible happened, would you care how it affected your family? The answer was easy when it came to your brothers and father. They were the bane of your existance and you couldn't care less about them.

You didn't lie when you said you were indifferent about Sanji. He left when you were all still young and then goes on his own adventure. He hadn't spoken to you in years and while there was no resentment between you two, there wasn't any love either. That settled your opinion on him. But then there was Reiju. She cared for you more than anyone else had. She was your anchor through the hard times and kept you from losing yourself more times than you could count.

But on the same note, her fear of the repercussions if your father knew how she interacted with you kept her distant in the presence of others. She wouldn't aggravate you mercilessly like your brothers, but she wouldn't stop them either. That made you question how much she actually cared for you. If she really cared, she'd be more than just a bystander and that's really all she'd been your entire life. Someone who looked on to your pain neutrally and comfort you in the shadows. That wasn't love.

"(Y/n). Do you care?" Katakuri repeated himself, not missing your hesitation.

"....I don't think I do. Is that bad?"

"I don't know." He answered honestly. "I'm a pirate. My idea of good and bad is a little different than most people's."

You smirked at that. He had a point. Your ideals were skewed as well so it probably didn't even matter.

"Then no, I don't care what happens with them."

"Then I can fill you in on what's really going to happen tomorrow." Relief flashed across his eyes. "I need you to pay attention to the plan so you can stay out of the thick of it. I've already talked to Mama about keeping you safe and she's agreed. No one will touch you as long as you follow directions."

He was kind as he went about detailing the events for the morning. And while you listened intently, another part of your mind was elsewhere, trying to piece together what was happening. You were giving up everything you'd ever known with the hopes that this almost stranger cared for you. If this was all one big lie, you'd pay dearly for it.

But as you watched Katakuri carefully, you knew you were willing to take the chance. If things failed, you'd go without a single regret. For now, you'd enjoy the moment and hold on to the hope that tomorrow would be the day your life changed for the better.

(A/n)
This one took me a while simply because of how love at first sight is usually portrayed. It comes across as cheesy in a lot of stories for me and while that's not a bad thing, it's not the direction I like to take for any of my stories. It was a great challenge to see if I could write that kind of situation in my own way and I hope it came out well. I did my best to make sure things didn't feel super rushed and it took me a few days to get it written how I wanted. There was a lot of writing small portions and then having to stop so I could think and come back to it.