Quite a few enemies dont have a sexing lose condition, even though they have lines for when getting penetrated.
Persephone, ettin, jester, puca, minotauress, wasp, dark knight and demon king come to mind. This, in essence, means you can ravish them indefinitely, except for demon king who cant be disarmed and base stats are high enough to be dangerous at any health level.
But its worth risking it at least once, if only so you can get a hilarious
endscreen that immortalizes Hiro molesting her like a blow-up doll.
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