Caught in a witch's spell (гет)

Harry made a promise the day his cousin beat him for the last time—just the day before his birthday—that no one would step over him again, literally or figuratively speaking.
At the time, he thought of it as something silly; he knew he was at the bottom of the food chain, after all.
And there wasn't much he could change overnight, even if he became a wizard. He was not tall, nor have any muscle. And really, he wasn’t the brightest of them all.
So when the pretty blonde at the robe shop showed a little bit of interest in him, it felt nice. Not many girls –if any, actually– had shown interest in him before. She was a little bit rude, but the predators needed that to stay at the top.
Just a slytherin!Harry AU