It is Faceless.
Narumi has silver strips of hair on the sides of his head, and even if they were temporary there is no plot device that would justify him trying to kill Shirogane, he doesn't have the character profile of jumping to kill even when he is being deceived by some information, Faceless knows about Shirogane's feelings he is trying to deal with them.
Edit: So i just remembered that Narumi might not remember Shirogane, so he may mistake her for Francine... well fuck. But i am still convinced it is Faceless with his plans.