"Are you googling how to get revenge?" Derek asked hanging over Stiles' shoulder and swiping a sweet from an open bag that was mostly scattered across the desk. At Derek's comment he quickly minimised the window.
"No," He replied sweetly as he leant back on the chair, his phone cradled between his shoulder and ear as he typed. It was more than a little unconvincingly.
"Stiles"
"Derek," Derek levelled him with a stare, "Consider it plausible deniability," he suggested. "Oh Danny, hey, hi, yeah, so how willing would you be to help a brother in need," Derek leant back on the desk and tried to decipher Stiles' notes as he bartered with Danny over the phone.
"What do you mean that's you're final offer. That's extortionate! Fine, fine you know what I'll agree to it and I hope it haunts your conscious," He hung up and threw the phone into the haphazard mess on the desk.
"Have you considered that maybe I wouldn't be opposed to helping you,"
"I've had an offer from Laura already," He waved towards an A4 brown envelope balancing on top of a stack of books." Blackmail or embarrassment material courtesy of her and your mum."
"My mum's helping you with revenge too?" Derek reached for the folder but was intercepted by Stiles plucking it from his hand before he had a chance to look at it's contents.
"She'd like me to ensure Cora won't date until at least 18,"
"By any means?"
"She didn't specify but I have my limits,"
"Really?"
"I'm going to personally humiliate her in public without connecting said humiliation to you or the rest of your family,"
"How kind of you," Derek drawled as he crossed the room to grab his homework from his rucksack and dropped down onto the bed, bouncing on his stomach and opened his notes.
Stiles watched him from the desk. Any other time he would look up and hold his gaze until one of them crossed the room and a subsequent make out session was inevitable. Derek was ignoring him.
"You don't want me to retaliate?"
"Not necessarily. Kind of like to know what it is you're getting yourself into," He muttered still not looking up.
"I can do this myself. Scott's got my back. I don't want pit you against your sister, I just want to get a bit of revenge," He clicked off his computer grabbed a pen from the desk and spun the chair round to face Derek, "You understand that right,"
"If I ask that you don't get yourself in too much trouble..." Derek started as Stiles pushed up and crossed towards him.
"I'll uh tell you not to worry," Stiles shrugged. Derek ducked his head back to his work.
"I can't not worry," He muttered into his books determinedly. He took a deep breath as Stiles dropped to sit next to him, "You go over the top and get obsessed. I don't want you getting hurt anymore,"
"That's nice but I don't need a protective bubble. She's got this coming," He leant over Derek's shoulder to correct an answer. Derek twisted, catching his hands around Stiles' waist and rolling them both further across the bed. "She is my sister. I actually like her when she's not being evil and malicious,"
"Duly noted," He nodded seriously before leaning in
The work scattered and creased under them but Derek paid it no mind as he lost himself in the moment of eliciting moans from Stiles and tried to forget how much trouble his boyfriend was inevitably going to get himself in.

It was the middle of the next week when everything felt very off from the moment Derek stepped out of the car at school. Firstly Stiles' jeep was already there. It was rare he was anything but just on time. Between him and Scott there was always one of them running late but the jeep was there. The second was the grin spread across Stiles' face and the third the side glances he and Scott kept sharing. Derek could feel himself mentally bracing himself for multiple worst case scenarios and when the bell sounded Stiles pulled him in for a kiss.
"You look on edge," Stiles whispered as people pushed past them heading inside.
"I know what you're capable of," Derek glanced warily up towards the main entrance
"Trust me, okay?" Derek nodded and Stiles pressed another kiss to his lips before grabbing his wrist and dragging him through the crowds. Derek could do little but follow his lead.
One of the first things he saw was a mock up wanted poster a defaced portrait of his sister staring down at him from its prominent position the archway right inside the main entrance. Wanted: Cora Hale
For the following Offenses…
And below that were half a dozen bullet points listing everything from bad language in front of minors to suspected larceny and personal defamation. Derek didn't have time to read them carefully as Stiles pulled him on through the crowds he saw other pictures of his sister carefully displays. Not in wanted posters but more like pages of a scrapbook littering the corridor's walls.
"Stiles, how many are there?"
"Okay I may have overdone it on the photos but the other pranks were just as fun and I really hope someone catches them on camera," Stiles grinned and as if on cue a scream cut through the noise of the students and the hallways fell silent for a moment. There was no mistaking the source of the distress. Stiles' grin had dropped but the spark remained in his eyes.
"I'd avoid your sister for a little bit yeah, you might get, uh, contaminated,"
"What?" Stiles merely shrugged.
"There was manure involved, and maybe glitter, but I've got to get to class. I'll see you later though right?" Stiles darted up to peck Derek's lips once more, "Love you," and then disappeared into the crowd.

Derek had turned his phone off by the time half an hour had passed, every couple of minutes a new text had come through asking if the pictures up around the school were real plus several from Cora all in capitals which he'd ignored immediately. Plausible deniability, never saw them, couldn't help, nothing to do with it. She'd brought this on herself.
The thing was, some of the pictures were real. The baby pictures, the Disneyworld pictures. Then others Derek knew must be photo-shopped but only because he was fairly sure she'd never dressed up as the little mermaid at age 14 and sat in the bath surrounded by Barbie dolls. There were dozens of pictures all around the school that people were sharing with each other. It was practically a scavenger hunt to find them all. Derek did feel sorry for her, and dreaded finding out first-hand how she was reacting.

By lunch time Derek was hiding out in the library. Ms Goodwin would ignore his eating up here and he desperately wanted to avoid the confrontation between Stiles and his sister. So at the risk of it occurring in the canteen during lunch he'd ducked out to the far corner of the library.
"Yo Derek," It seemed Stiles could find him anyway. Derek looked up to see his boyfriend leaning on the corner of a bookshelf.
"You're a menace, and if the texts I've been getting all morning are anything to go by my sister hates you,"
"Already knew that though right? Hey, do you want to get burgers after school?"
"Anything to avoid going home to Cora throwing a fit,"
"My treat,"
"You already had me convinced,"
"Yeah but," He shrugged, "We're alright aren't we. I didn't cross the line with what I did to Cora,"
"It'd take more than you embarrassing my sister,"
"Like what?"
"I don't know, cheating, killing someone, something really bad,"
"Got it. No really bad stuff. Right yeah. Not like that was going to happen anyway but y'know. Good to know those limits exist right?" Derek rolled his eyes, stood from the chair and took two steps towards Stiles before pulling him in by his jacket.
"You're overthinking something aren't you?"
"Well about half way through first period I remembered how you didn't actually want me to retaliate at all, and then I got kind of obsessed with the personal attack on your sister and if I'm with you at some point I've kind of got to be on good terms with her right I mean she's your family and…"
"The only person you need to be on good terms with is me,"
"But she's your sister,"
"And you're my boyfriend,"
"Mmm, still like the sound of that,"
"You said you loved me this morning,"
"Shit what? No wouldn't have been me saying I love all this," His hands slipped under Derek's shirt. "Can't think why I would say that at all-," Derek cut him off with a bruising kiss, pressing him up against the bookcase, a hand rushing to prevent his head hitting the shelf and carding his fingers through Stiles' hair.
"Tell me again," Derek's voice came out at a low rumble and Stiles couldn't help the moan that escaped.
"Love you Derek Hale. Your sister can suck it,"
"I'd rather I was the one doing the sucking," He whispered as he moved to kiss down Stiles' neck.
"You can't do that to me dude I'm so on edge right now. Ms Goodwin already gave me that disapproving look when I came in," Derek pulled away slightly to rest his head against the crook of Stiles' shoulder and felt the other boy let out a long shaky breath. Derek kind of knew he was pushing their growing boundaries; he wanted so much of Stiles whilst knowing they weren't entirely ready, still building on what they were.
"That's because every book you bring back is damaged," he muttered into Stiles' collar bone.
"Which is why I really can't get any further on her bad side,"
He could feel Stiles' heartbeat and smirked as he ran his thumb across the pulse point. It amazed him the way that racing heartbeat was all down to him. Stiles' reaction to him. He'd lie in bed at night and not believe it was real.
He felt Stiles' hand loosely slip into his own.
"Sorry,"
"Well one of us should be sensible," Derek squeezing Stiles' hand in reassurance.
"Who'd've thought it would be me huh?"
"Debatable," Derek smiled as he pressed another kiss to Stiles' shoulder as he was playfully shoved away.