Is there any zombie hentai? Vampires, ghosts, devils, succubi... yes, there's hentai about those.

Not zombies, though, as far as I can tell. It makes sense. Zombies aren't sexy. Having sex with one would be necrophilia, but more dangerous. If that's your preference, though, the nearest you'll find in hentai might be this. In a university hospital, experiments are being done with drugs, corpses, disturbingly insane people and (at least in one scene) resurrection. She was dead, but now she's alive. Also, sometimes you'll be wondering if the girl in a sex scene is alive or dead. She'll appear to be a fish-eyed corpse, but then she'll open her mouth and ask if the bloke's finished.

Episode 1 might be the most disturbing, because it has the fewest sex scenes and is more about its slow, ugly story. Yasaka Seiji is a depressed, morbid man who's about to start an unpleasant job. He's going to be washing corpses. They'll all be young, female and buxom (because this is hentai), but they'll also sometimes be grotesquely injured and Seiji's reaction to them couldn't be further from sexual arousal. Here's an example of his thought processes... "Something came up to the pool surface, accompanied by a weird aura. A vessel in the shape of a human. Eyes that will never open and a face that will never be seen smiling again."

Seiji's also being female-on-male raped by the hospital's Vice President, who makes him take mysterious drugs. He asks her to stop, but she doesn't. There will be weird visions. There will be corpse-scrubbing with a rough brush, after which Seiji understandably vomits. There will be highly accommodating nurses who want to show how much they like Seiji, but this won't end well either. Seiji's going strange and occasionally having scary facial expressions. Was he always sick in the head? He'd seemed afraid of himself, after all. Was it the drugs? Almost certainly, at least to some extent. The worst thing is that those nurses seem genuinely nice and don't deserve what this story has in store for them.

"I'm not done yet. I can't satisfy myself just with this. It feels good. Yes, I wanna see that face. That's it, the face that fears death. I wanted to see that face. Fear of death! You understand?"

Episode 2 is less disturbing because subtlety has been long forgotten, but it's even more gross. It starts with a nice girl getting killed and mutilated by a condom full of acid. Someone put it in her lunchbox. There will be rape. A bead spike releases a spray of green slime when it's eventually pulled out of a girl's anus... and our hero immediately licks the bead spike. No no no no no don't urgh. The sex scenes get ever more frequent, but there's nothing sexy about them. All they do is disrupt the plot and make the series feel less like a story and more like a sort of hallucinogenic collage of grossness. Episode 3 explores surgery. Cut off the breast, cut open the pregnant belly and pull out something from a nightmare. If this is Yasaka Seiji's subjective reality, then he's completely lost his mind from the drugs.

The post-credits sequence suggests that some of this was real. "The ten bodies of unknown identities that were found at the Sougou University Associate Hospital were discovered to have organs missing and bodies covered in a strange fluid, according to the results of the preliminary autopsy."

...but then there's one last horror twist. We haven't escaped insanity after all.

This OVA series is based on a visual novel that I'm pretty sure you don't want to know about. Was everyone here dead already? Is the human mind what truly gets corrupted? In fairness, the storyline's pretty unique and could even be interesting if you can take the drugging, enema play, cum, bondage, rape, gore, killing, inflation and necrophilia. I liked the nurses in ep.1, which is what made the series distressing. It would also be possible to have sympathy for Yasaka Seiji at the beginning, but he goes so scary-insane that your reactions to him will quickly become fear and disgust.

If you're looking for depravity, step right up. Normal people shouldn't consider watching this for a millisecond.