Yeah so I reloaded and tried 3 times to try and get every possible outcome. Once you have met the Vampire sisters and been inducted into the undead party club via drinking the redhead vamp's blood you cannot kill them. If you try to enter the crypt during the day the MC just says "I should let my mistresses get their beauty sleep" or something to that effect. I guess/Hope Tinkerer is just going to introduce their master later on and we get to kill him and become the master of the vampire sisters. Or maybe become his disciple or something furthering the MC's own Power, adding to his accomplishments you know him already being the Chosen one of Nergal and a Quetesh's priest.
Only way to kill the Vamp sisters is if you open up the crypt without knowing that the three fresh corpses in there are actually vampires. The scene had a subtle "GTFO Necrophilia" vibe to it. Since the MC opens the cofin a little and then see's three fresh looking corpses and still decides to open it further with the other option being Let them rest in peace. IDK doesn't fucking a vampire count as necrophilia ?
Eh... the Daughter might get him in trouble here too depending on how loli'ish she is, rule 7 on here would definitely apply to her, they initially kicked out Insexual Awakening and Urban X Demons... and the loli/shota there look cartoonish not that realistic but seeing how awesome the Art in this game is how descriptive and well made the faces of all characters are, they would definitely be considered realistic. I don't want this game getting the boot... I should probably look into that Site you mentioned and pray to the gods of Hentai.