Femtazio: How to Unlock the Last 6 Scenes of Fire Nymph?
Short answer
Suggested fix (unconfirmed): Lose to the fire nymph whenever she appears on the field. Complete all her missions while losing every time until she is finally released at the end.
No confirmed fix yet. Players suggest: EDIT: This is probably more luck than "solution", but replaying dropping the difficulty down to lowest and just ripping through the level counted as a win.
Suggested fix (unconfirmed): Keep the video scale at x1 in the options and avoid clicking the engine default restoration buttons in the in-game settings.