Kuro no Danshou

King of scary good hentais. I found it. 

While they're both horror series that are filled with suspense and violent content Oni-Tensei has a Yuri love story instead of the usual heterosexual coupling. Engaging characters and a focus on the descent into madness.  

Both of these had a horror element, victims getting kill and such, Necronomicon has a very good mystery to it also, kind of like the movie 'Clue'. Mix that with hentai sex scenes = great !! Heartwork is more focus on whom is going to be the next killer. So watch both if u like a little thrill with your hentai =)