The "stray Reimu" term used in this trilogy was an interesting choice of words. It was "nora-Reimu". Not "yasei-Reimu" (Reimu born in the wild), not "sute-Reimu" (Reimu who was abandoned), not even "gesu-Reimu" (scum/trash Reimu), but "nora-Reimu".
I used the simple "stray" reading for "nora-" but there's an additional layer to it. Calling someone a "nora-__" means you're calling them the equivalent of inbred trailer-park trash.
Judging by the Deibu's actions in this trilogy, I'd say it fits.