Oh, just a little bit...

Once you're fully dressed, you swipe the marker off your dresser and storm out of your room. You don't know where this surge of courage came from, but you don't care! Theresa's been asking for some comeuppance for years, and now you finally have the gumption to give it to her. For all she's put you through your entire life, she deserves whatever nasty, horrible thing that could come to mind.

...Or at least, that's what you kept telling yourself in your head all the way until you stood in front of Theresa's bedroom door. Could you really go through with this? Did you actually believe in this frantic **** plot you'd suddenly concocted? Divisive, you stare at the door for a while, weighing your feelings. You don't really want to hurt your big sister, even if she has been a total twat to you for as long as you could remember. Eventually your conscience wins over, and you let out a defeated sigh. This is exactly why people walk all over you.

You look back down at the marker in your hand. Maybe... just a little ****. Nothing major, just giving back a little of what she gave you the night before. That's harmless enough, right? It'll be a good message for her; that you're not going to just sit around and take it without repercussions. A good first step! Oh, but how mad is she going to be?? Is this going to turn into a vengeful cycle, exacerbating into an all-out prank war?!

Before you can psych yourself out again, you steel yourself and grab the handle of her door. Turning it oh-so-slowly, you open it just a crack and are relieved by what you hear. Snoring shamelessly, the girl was sprawled out across her bed, limbs poking out randomly from beneath her blanket. If she's sleeping in longer than you had, she must have been up awfully late scribbling all over you. Pushing in, you tiptoe over beside her, eyes scanning over her as you plot your next move. God, you're really doing this...!

In the dim light of your sister's room, you can't help but admire her in her most tolerable form: ****. Snoring aside, Theresa really is pretty when she's not sneering and jeering at you. It's a strange kind of familial pride you feel, knowing she takes good care of her body. Her facial features are soft and lean, framed nicely by a mane of wavy brown hair. Though closed now, she has a lovely pair of vibrant hazel eyes you've always been a little jealous of. Why did she have to inherit Dad's eyes and not you? Even under the blankets, you can see the contours of a large bust pressed upwards. They aren't the biggest you'd seen, probably a good C cup, but you also don't make a habit of comparing your sister's breasts to girls you actually had interest in. Narrow waist, toned abs, shapely long legs and cute little feet; it never surprised you that Theresa went through boyfriends like they were seasonal fashions.

Now... where to start? You very much want to return the favor and draw something obscene on her forehead, but you're also terrified of waking her up and invoking her ire while you're still in the room. Somewhere less sensitive... her arm? Yeah, that'll work. She has one of them oh-so conveniently strewn out right in front of you, so it's an easy target.

Steadying your shaky grip on the marker, you pop off the cap and bring the tip close to Theresa's skin. What to write? Maybe just some crude graffiti? Nah... something more personal. A message feels more appropriate. Yes, a declaration of your refusal to endure her nonsense any longer!

Grinning like a fool, you start to write. You go slowly, hoping your sister isn't ticklish on her arms, writing a short but sweet memo to your darling big sis for her to read when she wakes.

'This is war, sis. Time for some payback.' — Gavin Shaw

...Wait, why did you sign it?? This isn't a letter, you dolt, it's your sister's arm! Oh well, no way to take it back now. It isn't as if she won't know who did it, given you addressed her as 'sis.' Despite your flub up, you can't keep a satisfied grin off your face. It isn't much, but this is the start of a new you! A Gavin that doesn't just turn the other cheek! Let's add a little hand giving the finger while we're at it... No wonder Theresa thought of this idea, it's oddly fun!

Before you can continue your **** doodling, Theresa begins to stir and shuffle on the bed, letting out a groggy whine. Fuck, fuck, she's waking up! Abort mission, get out while you still can! You leap to your feet, abandoning the marker and beelining for the door and slamming it behind you. Theresa's surprised yelp on the other side makes you flinch, heart pounding in your chest.

"Who the fuck?!" You hear her call from within. Not daring to answer, you make tracks and escape toward the living room.

Sweat on your brow and a lump in your throat, Mom and Dad glance in your direction with a puzzled, concerned look across both their faces. Seems they were both relaxing on the couch, shoulder to shoulder, enjoying a previously quiet afternoon. Dad has a tablet in his lap, only barely paying you any mind. The acrid smell of one of his cigars wafts in your direction, stinging your eyes a bit. Ugh, such a terrible habit...

"Gavin sweetie," says Mom. "Is everything alright? I thought I heard Tess shouting."

You swallow hard, trying to calm your breathing. "Oh, u-um... yeah, it's fine. I went to wake her up, and I guess I startled her."

" 'Bout time," Your father grunts, eyes going back to the news article on his tablet. "Wasn't sure you two were ever gonna wake up. I know it's the weekend, but you missed breakfast. Don't start gettin' lazy on us just because you're a senior this year."

"Oh, let them rest while they can, dear." Mom gave you a comforting smile, patting her husband's leg. "Tess is already in college, and Gavin isn't too far behind. Let them be kids a little while longer." Dad only responds with a grumbling sigh, unwilling to push the matter.

You crack a smile as your tension eases a bit. Thank goodness Mom is always there to be on your side. The passage of time has been good to her, age not wearing away any of her innate beauty. While it might be a blessing for her (and your Dad, you suppose), it's always been a bit of a curse for you. Many a time you've had to avert your eyes while she takes care of the house, always wearing those sleeveless tanks that leave a swath of cleavage exposed from her tremendous bustline. Even if they've drooped just a smidge, they still look creamy smooth and full, often bulging out of a tight bra. You can't half stand it when she bends over to get something off the floor, the fabric of her pants straining to contain those wide motherly hips and big, round ass. Dad's a lucky bastard, alright...

Today's mental broadcast of shameless, incestuous daydreaming has been interrupted by a special announcement. Theresa, still in her room, has just let out a shrill scream, causing the rest of you to startle hard and look in her direction.

"What the hell?!" your Dad calls out incredulously.

"GAVIN!!!"

Wuh-oh. Here it comes.