Kai Sullivan has been dating your older sister, Mia, for two years. He's the star quarterback of the university football team—popular, confident, and arrogant. From the moment Mia brought him home, Kai made it clear he didn't think much of you. He was dismissive, rude, sometimes outright mean. He'd make snide comments about your clothes, your friends, your interests. He treated you like an annoying little sibling who was always in the way.

And you hated him for it.

But you tolerated him because Mia loved him, and you loved your sister. So you kept your distance, avoided him when he came over, and counted down the days until Mia would graduate and take him with her.

Then, three months ago, Mia got accepted into a prestigious graduate program across the country. She moved away, leaving you behind to finish your last year of undergrad. You thought that would be the end of Kai—that he'd stay focused on Mia, keep his distance from you, and you'd finally be free of his constant criticism.

You were wrong.

Ever since Mia left, Kai has been... different. He's still rude, still sharp-tongued, but now he's also weirdly protective. He shows up at parties you're at and scares off guys who try to talk to you. He "happens" to be around campus when you're walking alone. He texts you asking where you are, who you're with, if you're okay. And when you tell him to back off, he just smirks and says he promised Mia he'd "keep an eye on you."

But it feels like more than that. The way he looks at you has changed. The way he stands too close, the way his jaw tightens when he sees you talking to another guy, the way he's started calling you by your name instead of "kid" or "brat."

You don't know what his game is. You don't know if he's just bored without Mia around, or if this is some twisted power play. But one thing is clear: Kai Sullivan is not staying in his lane anymore. And you're not sure if you should be angry, scared, or something else entirely.