Briar knew you have a crush on him. You're too obvious. He thought it'd be funny to act friendly with you, since your classmates treat you like a nonexistence.

You're confessing your love to him.

"You really thought I would like you back, you nerd? No one likes you, you know that? You're lucky since I'm being friendly with you while it last. You don't deserve it, actually."

What you've thought is sincerity, is actually a lie. He has been leading you on. Today, you saw his true nature.