Summary: A woman goes to Vegas to get over her abusive ex and ends up accidentally marrying Sebastian. Inspired by Last Name by Carrie Underwood.

Last Name
A Modern Black Butler AU – Oneshot
Vegas at night was all neon lies and second chances.
Sebastian Michaelis loved it.
From the balcony of their hotel, he watched the Strip pulse like a living thing while Ciel Phantomhive sat behind him, laptop open, already irritated.
“Try not to get distracted,” Ciel said flatly. “We’re here on business.”
“Of course, my lord,” Sebastian replied smoothly, straightening his jacket. “Though Las Vegas does have a way of encouraging… spontaneity.”
Ciel narrowed his eyes. “That was not reassuring.”
She hadn’t planned on Vegas fixing anything.
The trip was supposed to be loud distractions, cheap cocktails, and friends who refused to let her text her ex ever again. A clean break. A reset button. That was the goal.
She stood out even in a city built on excess—natural red hair spilling out from under a black beanie, smudged eyeliner, combat boots paired with a dress that screamed bad decisions incoming. Emo, unapologetically so. Funny without trying. Sweet in that way that made strangers open up without meaning to.
And a bit impulsive when drunk.
Okay—more than a bit.
By the time she bumped into Sebastian Michaelis at a hotel bar, she was already two cocktails past sensible.
She nearly spilled her drink on his immaculate suit.
“Oh my god—sorry—wow, you look like if a funeral and a fashion show had a baby.”
Sebastian blinked once.
Then he smiled.
“No harm done,” he said. “Though that may be the most creative compliment I’ve received all evening.”
Her friends immediately abandoned her.
Traitors.
Sebastian wasn’t supposed to be chatting up strangers. He was supposed to be keeping an eye on Ciel, following leads, maintaining professionalism.
Instead, he found himself laughing—actually laughing—as she told a dramatic story about dyeing her hair black in high school, crying because it didn’t “match her soul,” and then immediately bleaching it back.
“You’re very dramatic,” Sebastian observed.
“Only about important things,” she replied solemnly. “Like eyeliner and emotional healing.”
He liked that she didn’t flirt like she had something to prove. She didn’t ask what he did for a living or why he looked like he stepped out of a magazine. She didn’t treat him like a mystery to solve.
She treated him like a person.
And when she mentioned her ex—briefly, carefully, with humor masking something raw—Sebastian’s amusement softened into something quieter.
“Sounds like you deserve a better chapter,” he said.
She lifted her glass. “To better chapters.”
They clinked drinks.
That was when things started to go wrong.
Or very, very right.
Vegas blurred beautifully.
A dive bar with live music. A dance floor that didn’t care if you were bad at dancing. Laughing too hard. Singing songs she didn’t quite know the words to. Sebastian somehow knowing how to lead every step, every moment, like the night itself bent around him.
At some point, she looked up at him, eyes bright and unfocused.
“You’re dangerous,” she said.
He raised a brow. “Am I?”
“Yeah,” she nodded. “You make bad ideas feel… safe.”
Sebastian, who was quite literally a demon, found that unsettling.
And intoxicating.
She woke up with a headache, glitter on her cheek, and the overwhelming certainty that something had gone horribly off-script.
The hotel room wasn’t hers.
The suit jacket draped over the chair definitely wasn’t hers.
And the man sleeping beside her—
She sat bolt upright.
“Oh—oh no.”
Sebastian stirred, eyes opening calmly, like he hadn’t just detonated her life.
“Good morning,” he said pleasantly.
She stared at him.
Then at her left hand.
Then screamed.
“There is a RING. On my FINGER.”
“Yes,” Sebastian said. “That would be because we’re married.”
She clutched her head. “I DON’T EVEN KNOW YOUR LAST NAME.”
Sebastian paused.
“…That is an unfortunate oversight.”
Ciel arrived ten minutes later, took one look at the scene, and pinched the bridge of his nose.
“You got married?” he hissed.
Sebastian nodded. “It seemed appropriate at the time.”
She waved awkwardly from the bed. “Hi. I’m the mistake.”
Sebastian smiled at her. “I wouldn’t say that.”
Ciel looked between them. The ring. The marriage certificate on the dresser.
“…We are never letting you drink again.”
Later—after coffee, apologies, and several long conversations—she expected regret to crash down on her.
It didn’t.
Instead, there was laughter. Gentleness. Sebastian asking what she wanted, not assuming anything. Not trapping her. Not controlling her.
For the first time in a long while, the future didn’t feel scary.
Just… unknown.
She looked at the ring again, then up at him.
“So,” she said, “you gonna tell me your last name?”
Sebastian chuckled softly.
“Michaelis,” he replied. “Sebastian Michaelis.”
She smiled, slow and real.
“…Yeah,” she said. “That sounds like a last name I could get used to.”
And for once, the bad decision felt like the beginning of something good.