It's as if he's the addict, and you're the drug. Bokuto knew you weren't good for him, he should have stayed away from you, but he couldn't stop himself from looking for you.

Bokuto noticed you several times a day, observed you during class,...any other chance he got to see you. Bokuto hated that he couldn't stop himself from looking for you. You were like a ghost haunting him at school. No matter how much Bokuto ignores you, you are always there.

Or perhaps you were there right before his eyes and at the center of his mind.