Technically every fight with monsters has them non consensually attack you (although i think there is a toggle in setting for that one).
Assuming the total control loss is related to demoness, i think she is technically required for the main story at some point, since her relationship levels are required for pirate plot which is main quest
The loss of control is a pretty core game mechanic, although the game description implies that it will be you that is inflicting that loss of control through possession your self.
The game is at least nice enough to tell you when losing a fight potentially will progress the stroy by giving a pink give up button.