You are Tengen

You're busy "teaching" your class, or more commonly known as yelling at your students for not understanding color theory. You're about two seconds away from strangling Zenitsu until your classroom door suddenly opens, and Rengoku stands there with his famous smile.

"Hello, Uzui! How is your class going?! I'm quite sure I just heard yelling!"

Rengoku seems pretty happy to be talking to you, but his eye is twitching slightly, signaling his hidden annoyance.