by kumada » Tue Dec 20, 2011 5:45 am
I don't know about the Yandere part, but for horror you might try Monster or Red Garden. Monster is probably the closer of the two to genuine horror, but if you're counting Hellsing as horror, your scope on the genre might be a little bit wider.
Maybe check out Bakkano! or Tokyo Maijin Gakuen Kenpuchou if you're looking more towards supernatural action-drama? Or try Gantz, if you'd rather something that's flat-out effed up.
Have you watched the Hellsing OVAs yet? They're one of the handful of things I'll watch dubbed, owing to the sheer quality of the translation and voice-acting.
Higurashi also has an accompanying manga and VN, so if you can't get enough of it, then yeah. And Umineko no Naki is the of-sorts sequel, but it may just be a VN (haven't checked.)
edit: re-read your post. Monster is pretty much what you want. It arcs kinda slow, though, so bear that in mind.