i would like to point out the good end doesnt require your sex slave and slut rate to be 0%. you just need the sex slave rate to be higher than your slut rate. i sorta did the demon lord end first because fighting monsters naturally will raise her slut stat and it ended higher than her sex slave stat when i reach the throne.Good end: have sphilias slut rate and sex slave rate at 0% and go beat the game,
Demon lord end: either have her stats high or just choose the bottom option at end and beat the last boss.
NTR end: after beating the game once, get NTRd and then go to demon king castle.
Epilogue: after completing the game(maybe good end) start a new game and select epilogue
the demon lord end option is locked if ur slut stat is higher than your sex slave stat. as far as my playthrough went.