Classical Western monsters (goblins, dragons, fae, and the like) represent threats from outside: the unknown, the inhuman, the wild. 化け物 "bakemono", the common and well-known Japanese word for monster, at it's etymological core means altered thing. It feels like there's an added nuance there; an acknowledgement of the monster within. Or maybe I'm just reading too much into it.
... you wraiths!It was as we suspected.Yes, I will leave the details to you.Farewell.NagatoPutting her under surveillance was the right call.