[kattywhy]

I know it's really few details but I only watched it once a long time ago.

It's in some kind of fantasy setting and theres a male main character that is up to no good. There's some kind of big monster that takes energy from abducting girls and the female character is some kind of demon mistress in charge of the monster . There are tentacles involved and in the later episodes the male end up screwing the demon without her consent so it was like a forced sex.