The jig is up! Oh well, time to kill the baddies.
Edit:
I just noticed that, while Credo claims that those cursed by the Ethos Book cannot be hostile to each other, didn't he just attacked Yuuji the
first time they met back in Ch.75.1? If it is then maybe Credo already knows Yuuji was an infiltrator from the very start and only feigned ignorance until this very moment? His "wasn't a serious attack" excuse for his assault at Ch.75.1 sounds very dubious though.