Jump in and interrupt them

You've had enough of this. You're both adults now. He can't hurt you anymore. Not unless you let him steal your girl. You walk up to him and act surprised.

"Derek? Is that really you?" You ask.

"Adam?" He asks back. He looks completely caught off guard. He doesn't know how to react.

"You know it, man! What're you doing here? I thought you were off in a big city."

"Oh uh...well I was but the business world there is pretty full. No room for a beginner to try his luck," Derek answers.

"Well it's good to see you. You look great. Oh and don't bother apologizing for all the awful crap you did to me in high school. It's all water under the bridge," you say, ensuring Tori can hear you.

"Wait, this guy is the bully you told me about? Dude, you had some cruel ideas of entertainment back then," she comments.

"Yes, well we were just kids ya know? I thought I ruled the world back then. I got a bit carried away," Derek says defensively.

With his charm neutralized he cuts the conversation short and orders his black coffee to go. While Tori is pouring it, he grabs your arm and whispers into your ear.

"This isn't over."

"Game on," you reply confidently.

Derek takes his coffee and sulks out of the restaurant. You probably should have been less antagonizing toward him but it did feel good to best your tormentor for once.

Tori and you talk some more, mostly about how brave you were, and then you head out to go to work.