Someone who plays the game at a normal pace or, more generally, the legit way won't be able to get the required amount of Eros fast enough (unless we're talking of someone close to a day one player), plus, I remember the dev stating something along the lines of it being a troll ending. More importantly, though, like you said… the user specifically asked: Aren't there any game overs where a monster girl takes me as her permanent slave? >_>
The only game over which fits that description is Dark Perpetua's, currently. The suggested candy shop one could be considered a soft ending, but even that's a stretch.