To be fair, poor choices are kind of the hallmark of the entire community. -_-
"Dangerous demon that poisoned an entire city? Let's keep him in the cellar for a few hundred years and not tell anyone!"
"Reuniting the pieces of said dangerous demon, that were kept apart for the express purpose of keeping it under control? But of course, teacher! If you tell me my family are a bunch of traitors, it must be true!"
"Giving an incredible powerful, soul-destroying demon to a little kid who hates controlling demons? What could possibly go wrong?"
Seriously, who decided to give them any kind of power in the first place.
The Order did, because they're chronically short of Exorcists, and suddenly gaining who knows how many new Exorcists must've seemed like divine providence. They probably reasoned that they could easily bend the Myou Dha to their will, too, given that their leader was a sot who didn't even want to join the Order and commanded little respect.
To be fair, Mamushi thought they were going to take the eyes...somewhere else that wasn't back into the Impure King.
And with the families being the idiots they are...yeah she was going to trust the teacher over them.
Specifically, Toudou had convinced Mamushi that they were going to take the eyes AWAY from the purview of Mephisto, whom he'd revealed was "raising the son of Satan in secret." So he painted Mephisto as the real villain in all this. To Mamushi, Toudou had always been the kindly old teacher, and she'd probably confided in him a lot during her high school years if she had trouble with her family.
...sorry, I think I kinda derailed us here. This thread is supposed to be about Shima. :'D