Okay, am I missing something? Why the heck is LITERALLY NO ONE in this whole thread talking about why Miko isn’t telling Seto at the diner that THAT WAS HER DAD THAT HE ALMOST EXORCISED?!?! Does she not wanna give too much info?? Is it because she thinks it’ll make him want to kill her dad even more?? Why isn’t she saying anything after she nearly lost her dad for a second time???
Because, generally by Japanese lore, there's no good reason for a spirit to stick around after death. If it's sticking around, then it's already bad news or will inevitably become bad news later.
Now, that's not a pure rule, but we already know that Seto is a "Gotta kill them all" guy -- knowing it was Miko's dad would probably just make him more determined to eradicate it. (Though actually, he probably already suspects that.) Anyway, telling Seto "That's my Dad!" can only make things worse, not better.
(Note: we already know that some ghosts can stick around temporarily for good reasons. E.g. the guy who passed on the code to his safe, the mother and daughter waiting for their husband/father. And obviously, her father seems fine for now. But Seto doesn't think that way. Recall the way he eradicated the little girl ghost in the subway despite Rom's objections.)
