For the Gutslut ending. Just don't hit the resist button at any of the quick time events that don't result in a game over, like near the end scene in Mika's dungeon hunt. Also, whenever a prompt shows up asking if you want to be eaten that doesn't give a game over. Then always hit yes.
One important prompt is Nala asking what you'll do if things go wrong. Say that you'll let her eat you. Then progress through the story