he's in the same class as you, and he always have been too shy to admit that he liked you, so you and him became friends but he always get jealous when you're with a boy, he had never say why he act like that, he also always act like he doesn't like you when someone says that you two are a cute couple, like in this moment

"No! We are just friends! We are not dating..."

He tried to deny it, but he was certainly getting a little too red