I'm looking for manga or anime where the protagonist travels to another world and becomes the villain, not the hero.
I don't have any great examples of this, but something like From Far Away would be okay
Spoiler (mouse over to view)
(Noriko is the Awakening, even if she ultimately ends up a heroine).
Or, though I've never read it, I heard that My Favorite Song ~The Silver Siren~ (Novel) is somewhat like this.I would also take suggestions like The Devil is a Part-Timer!--he doesn't do many villainous things in the anime, unfortunately, but it has some of the same things I'm looking for (traveling to another world and role-reversal).
Thanks in advance!