For a fairly milquetoast isekai power fantasy manga, these assassins are consistently written pretty well without being going the "Eminence in Shadow" kitschy route. I mean the whole, appear out of nowhere schtick designates them to be used whenever backroom drama needs to happen away from the MC... The proverbial "get out of jail free" card whenever the writer has put themselves into a dull corner.
But... Understanding they still need some public display of guilt vs just eliminating things, and knowing that slaying after the public damage is done means few will ask any questions... well that is already leaps and bounds beyond most isekai assassin type side characters.