You can read the long discussion we have for the depth, but long story short - it seems like the dev was absolutely determined to make a really grindy combat game with a complicated story, that featured some porn as a teaser to get people into it. Instead of a hot porn game that featured the other stuff as a side aspect.
Hahahaha!!!!!! I KNEW this steaming dumpster-fire would eventually be Abandon! The dev refused to change anything about it no matter how much the fans said they didn't want the grindy shit.