The vague shape in my head feels... halfway to Ryslig/DDS territory, but not with the 'and now your meals are humans,' if that makes sense. (Not here for the cannibalism angle. XD)
Probably something keeping it from being Obvious outside of the Metaverse... except to other people who also know. Suddenly makes things with Akechi very interesting.
What it does make me think, though; MP's monsters came from some kind of Science Organization doing Weird Science or the characters running into the effects of said Science out in the world.
Side arcs probably include Ann trying to figure out if she can still have a modeling/TV/generally public-profile career. (Akechi: It's fine, people are dipshits.)
I feel like Yusuke and Haru in particular would lean into 'at least if someone looks like this you know where you stand, the worse monsters are the ones who look perfectly pleasant.' Probably also Ann.
More thinking on 'at what point would monster have happened to people': Anyone could go monster. Most people never do. It's easier when you're in a Cognitive Weird Thing.
By the ~modern age it's probably mostly considered a myth, that that can actually happen to people. But it does. When it starts happening on 'average Persona party size' scales, something's fucky.
(It has absolutely occurred to me that 'anyone can monster, most people never do' provides a little wiggle room for non-party members to get in on the fun. XD)
Suddenly makes things with Akechi very interesting.galaxy brain: Morgana is SoujiYes good, he DOES love cats.