Cruel King by Rina Kent:

He’s no fairy tale king.

Levi
Here, little princess. I’m your king.
You have three rules.
Bow. Break. Bend the knee.
Fight me all you want, but soon enough, you’ll be chanting long live the king.

Astrid
One day I’m Royal Elite School’s small fly, the next I’m hunted and left to die.
He doesn’t only shred my life to parts, but he’s also coming after my heart.
He thinks he broke me, but the new princess will bring the king to his knees.

Cruel King is a complete standalone prequel in the Royal Elite world. No book should be read prior to this.
This is a mature new adult romance and contains dubious situations that some readers might find offensive.