I thought I knew the answer... clicking a checkbox should normally indicate you want to see the thing you're checking.
But then I haven't seen a Futinari even though I had checked the box.
So, I'm going to try checking only the things I don't want to see and get back to you once I get far enough in to see if that changes anything.
Edit: Made it as far as the dungeon, haven't gotten to goblin boss, no sign of Futinari with the box unchecked. No sign of Futinari with the box checked.
Femboy succubus still a femboy in second anatomy class with the box for femboy unchecked as it was with that box checked.
So... I am going with my original assumption that a green checkmark in a box means you want to see that, and there just isn't a lot of that content out there yet.