i think it's clearly what the author want to do with seto "i'm the judge, i'm the hammer" sorta thing while romm so far always have better judgement than anyone else.
the shrine arc prove that romm was right all along but he's too weak to do anything at the time and all other incident he accurately tell which ghost are evil which aren't, how the forest spirit are there to protect and the old man are really really dangerous.
the Station scene prob kinda want to nailed on which ideology they're standing on
the theory of the longer they stays the corrupted they are became is something i was thinking about for a while but the hospital mini-arc kinda debunk this theory.
the mother and daughter passed away early on the dad's life, so they are lingering around atleast for 20 years or so. i think some are easily corrupted if they are evil from the very first but the good people are remained intact until their business are over.
oh yeah, the bald cat lover wife also stay with him uncorrupted, i think only the shrine maiden are succumb to evil even though she's seems like a good person because the circumstance of her death are unethical at best
there's so many stuff to theorize, mieruko and kaya honestly one of fav horror that still ongoing im looking forward for their new chapter release
My theory is that a ghost form has nothing to do with good or evil and more to do with how well they can maintain their emotions & sense of self
Miko's dad, Nyakuza dude's wife, & the hospital family seem to have accepted their deaths pretty easily & are just waiting on their families
The safe combo ghost didn't seem to take it too well & became fixated on said safe combo. Since it seemed to be more worry than anger, it lead to a slow decay until the numbers were passed on, then he was able to move on instantly
Mantis Mom was obsessed & resentful in life and this carried over, twisting her form. There is also the chance that dealing with the resentful spirits of the cats also pushed her mutation along
The Fox's familiars seemed more like they were being controlled, with their appearance being influenced by their controller. Once reminded of her past, she was able to break free, even for just a moment
The little girl is a good example in that I doubt she was a bad person (not impossible, but we got nothing to go on), but she didn't even know her own age, much less what was going on. She was frightened & was already showing signs of decay. Given time, she might have become like the balloon boy: calling out for help & aggressively perusing anyone that eventually reacts