Prologue:

Stefan wasn't sure how it happened.

It all started on that dreary summer night when she returned from college to visit home. There was something about the confident smirk on her face, the click of her heels on the drenched pavement...

She drew him in like iron to a magnet, like a mindless bug to a blazing light. He couldn't stay away even if he wanted to. He hated her, deeply and passionately, and he couldn't get enough.

He didn't know why, but he was hopelessly in love with his girlfriend's sister.

...

Katherine had no idea how it happened.

All she expected over summer break was to see a few old friends, drink a few martinis, and visit a few bars. Meeting a guy was not on her list nor was it something that she wanted. Yet, there he was on that rainy Saturday, with his gentle green eyes and handsome face...

It didn't matter if he was younger than her. She wanted him. And he wanted her. She knew he despised her attitude, her view on life, and sometimes she hated him too. But none of that was important; they couldn't stay away from each other and there was nothing either of them could do about it.

Whether she liked it or not, she was insanely in love with her sister's boyfriend.

...

So now, here they were, out on the porch of his old victorian house, their lips in a desperate battle for dominance. It was wrong; it was so wrong, but it felt so right. Neither of them could recall exactly what had led them up to this moment; did it really matter?

Nothing mattered. Except for Stefan and Katherine.

His heart was racing and her mind was reeling when they pulled away, breathing so heavy that they could feel each others' breaths on their lips. Beginning to shake, he whispered her name.

"Just kiss me," she demanded heatedly and desperately, gripping the back of his hair tightly, allowing their lips to collide again. He instantly complied. This was crazy, wild, out of character for both of them though it only seemed to add to the thrill. Stefan should have been anywhere but there; he knew that, but oddly, he didn't care. Katherine shouldn't have been wasting her time with someone as simply complex as Stefan, but it didn't matter. She was his and he was hers.

The moment wasn't broken until someone gasped in the driveway. Both pulling away to turn their heads, they were met with angry brown eyes.

"How could you?"

AN: I hope you liked the beginning of this story! This fanfic will be AU, so Stefan and Katherine will both be human. I've been having serious writer's block lately, so I figured I'd try writing something a little different, like Steferine :)

I hope that you all enjoyed this and thank you for reading! Please review with your thoughts (what you like, what you don't like) and let me know if I should continue!

Thanks! XOXO :D