While it's not a secret anymore that Levi and Erwin are (somewhat) together, none of the soldiers dare to talk about it. And every time a new batch of recruits join the Corps, it only leads to awkward stares and questions. Tired of putting up with it, Levi decides to not explain anything anymore, figuring it should be obvious enough to anyone who wasn't blind, and if they cared that much they could ask anyone else for all he cared.
Of course though, Levi has trouble expressing himself, and instead becomes a nervous wreck. Havoc ensues.