It's the same day as this conversation, and Erwin is waiting for Levi when he gets home.

"Hello, Levi." He practically pounces on him as soon as Levi enters the cottage, taking his cloak from him so he can get his shoes off. "I have an idea for us."

No beating around the bush, no small talk. Erwin is excited about something, and he's going to make it Levi's problem.