She's pretty much regular Shamiko who was mindwiped and then lied to about her entire life. Told only the bad parts about her life and that Mahou Shoujo's were to blame, told that Ryoko and Seiko would grow to hate her if things kept going, if she wanted to be a good girl she had to destroy the scriptures and invade the town, had to be a proper demon. She was constantly producing monsters made out of pure depression energy.
Even at her most evil all she wanted was five trillion dollars and unlimited all you can eat pancakes, and a good life for her family.
Machikado cast had their bonds destroyed, memories of each other erased by the villain. And they were pit against each other, just so Shamiko would be driven to depression and create monsters or something like that.