Really not that much of a grind until you see the last missions, and because unlocking CG's is nonlinear you can just get the expensive, impressive ones first.
Not that bad a game, though content gets limited pretty fast. My main gripe is that the game inherently favors you going to the bonus rooms over the actual monster fights, because you not only get the same or more rewards out of the bonus rooms, they boost your stats as well. It's usually favorable to spend layers 10-19 just killing rabbits, mining, picking berries etc. which feels weird and cheesy.
It's also weird that grinding Corruption is faaar harder than grinding Faith. The former you can only do by masturbating and losing through sex, whereas holiness gets boosted every time you successfully resist. It's a game where you get more chaste the more times you get raped lol
