Who the hell promised Miko forever? It wasn't what she wanted when she was turned into a Devilman. Transformations meant she could shed her old skin on a body taken for granted on the track team; as a result no doubt only Miko could see, being overlooked held her back. All she wanted, if she was going to be honest, was a way to be seen for someone worth noticing, someone worth idolizing. Physical power meant she could loom over those who didn't see her, didn't pay attention to someone who was always trying too hard to vie for attention she feared couldn't be reached.
Forever trapped in this body that wasn't exactly her sent shivers down her spine, sent her skin crawling. Permanence made Miko wince, but it was something she had to live with; the promise of an eternal, omnipresent "always" felt good in the moment. She coasted on euphoria during her first transformation, and there was something about the contortions of losing her humanity that made Miko a little too excited.
Then came the crash. No one recognized her for what she wanted to be seen for: a runner who brought people to their knees in awe, better than Miki Makimura who all too frequently stole the spotlight. Now people ogled her for her body: her powerful legs, curves filling out in the right places, and her braided hair like a horse's tail.
Was this torment called regret? Always lasted too long, and Miko had to wallow in the grave she built for herself, and no one could stop her (even if she asked for it).