Based off JustLetMeBeOkay's headcanon: Rukia never swears, except around Ichigo. Then she is a foul mouth shit because she feels she can let her rough side out around him. She used to around Renji when they were kids bur ever sense she became a noble she's stopped even round him. Oh and ichigo finds it amazingly hot and intimate.
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Moment's silence
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Ichigo realizes early that Rukia has a potty mouth. Or would, anyway, if she let the words come out.
It's kind of hilarious.
Whenever things go belly-up, she'll yell and scold and there'll be little pauses in between where shit and fuck would slot easily and carelessly into place, and despite the gravity of the situation, or the annoyance at getting lectured, it makes him grin a little because Rukia has a whole Thing going on: ladylike, prissy and proper, and knowing that she's actively censoring herself means she's more of a brat underneath all that then she pretends.
Sometimes, though, the deliberate gaps create spaces for questions: like why she's hiding, why she's pretending, who exactly she's censoring herself for.
He gets his answer after Renji and Byakuya, and Soul Society.
There, in front of people who have known her for lifetimes, Rukia is the perfect lady, above reproach in every way - perfect and emotionless and cold, taking her punishment and her abandonment by her supposed-loved ones with quiet grace and dignity. And Ichigo hates her.
He's seen her stifle obscenities when things frustrate her; has seen her physically clamp her jaw whenever she's yelling at him with the accusation that he was being careless; knows the exact colour of eyes when she's this close to swearing him bloody.
And whoever this girl is, she isn't the Rukia he knows.
But she's got the same spill of dark hair; the same slight, bird-like build; the familiar shade of blue eyes; the rosebud mouth, and then she's whispering, "Fuck, no."
He almost falls over, and given that he'd made quite an entrance on the bridge, and then proceeded to hurriedly walk past her because he couldn't come up with anything to say, it's safe to assume that Ichigo's lost enough cool points as it is.
It doesn't help that he's mentally pictured all the ways Rukia would finally get the words out, some in not so PG ways, but that's between Ichigo and his right hand. Likelier though, Ichigo always expected her getting the words out because she'd just been too indignant to stop it; she'd be loud and scolding, and a general pain in the ass.
Instead, Rukia holds her body tight, scared and small; there's a subtle tremble in her limbs. Ichigo's never seen her like this. And when she finally looks up to meet his gaze, her waterline is rimmed pink and she's-she's crying. But if he thinks she isn't furious, he's got another thing coming, "You idiot, you fucking idiot. You shouldn't…you shouldn't be here! They'll…they'll kill you!"
"I'm saving you," he protests, suppressing the urge to sigh and grin at her as her frosty exterior melts before all and sundry; her eyes spark, her knuckles are going white, and everything about her says she'll murder him in his sleep. Ichigo's never been so relieved, even as she explodes: "What did you think I was doing, you jackass?!"
Rukia doesn't wait for a reply before she's off on a tangent; cursing Urahara and Yoruichi, and ordering Ichigo with threat of bodily harm, made more graphic with every tense of fuck and shit she can come up with that is both grammatically correct and vivid as hell, and telling him to go the fuck home.
If he cared about anyone else, he'd notice that Renji and Byakuya look visibly thrown by the language, as it stands, all Ichigo knows is that he looks stupidly in love.
It won't be the first time Rukia actually swears at him.
She doesn't bother to pretend she doesn't do that anymore, though she pointedly doesn't do it around anyone else.
And while he's relieved that Rukia doesn't find the need to filter herself around him, at the very least, Ichigo can admit he much prefers it to when she's sighing the words into his skin, or gasping it at the ceiling.
A/n: Hang out or send me a prompt on my tumblr at everything-withered