The Urotsuki

Both anime have similar animation, and a similar dark and gritty tone. Both anime were release the same year in 2002. Urotsukidoji: New Saga and Demon Lord Dante deals with demons killing humans and evil forces that are trying to start the apocalypse. They also have a good share of blood, gore and gratuitous nudity. The main differences between the two is that Urotsukidoji: New Saga contains graphic scenes of sex and rape while Demon Lord Dante doesn't.  

Both are hentai from the early 2000's that are pretty story driven. Both titles are set in a school that has scary monsters, blood, gore, and violence. They both have similar art and animation with a very dark atmosphere. If you enjoyed one, you will enjoy the other. 

More from same director. 

Way better anime with much better animation and gorey violence. No tentacle rape, but real scenes that actually pertain to story. 

Blood, violence, sex, demons