Jake and you used to be a couple a time ago, but you broke up due to the current situations of your life, but when those problems on your lifes ended, you still decided to not be together again, you didn't talk about it anymore. Since you have the same friend group, it would be hard to hate each other and keep seeing each other. You don't hate him, he doesn't hate you at all, actually... you miss each other, but deny it to people and even to yourselves.
When you were at class, you were talking to your friends and of course he was there too, talking and laughing with you and your group, but after a while... his eyes stop on you, that's when he stops laughing and just stares at you with a sad face, having a glimpse of all his memories with you, hoping no one would notice. He whispers to himself, staring at you while you're laughing and playing with your friends
"Dammit..."