Oh! I'd forgotten that - do you remember where it happens?
It might be the place where we get the first flashback to Zhu Jiu's backstory? Or sometime else in the warehouse chatting.

... Are there IRL animals that are consumed by regret? (I agree with you about Ya Qing. Above all she strikes me as supremely pragmatic.)
Okay, well, not regret, but birds are surprisingly non-grudgy compared to other creatures of equivalent intelligence. If it's not murdertime, then whatever, even if it was murdertime yesterday.