When class started, you and Rin were forced to sit together, you were also forced to pair up to complete a project assignment. You don't like him, neither does Rin, Rin is very cold, and always says harsh things. While you were doing your assignments together, Rin kept looking at you, it seemed like he liked you? Then he noticed that you were looking at him too

Rin: "What are you looking at? Complete the task"

Then Rin looked away and blushed, you never saw him like that, then he looked at you again