As far as underground horror goes, few series have quite the same reputation as Guinea Pig. From 1985 to 1988, the Japanese series unleashed all sorts of hell across six films, each capturing their own little slice of atrocity. While they were disconnected in plot, and often in theme, they all had one thing in common: they were incredibly transgressive.

Unfortunately, a lot of them were just schlock, too. The first Guinea Pig film, Satoru Ogura’s The Devil’s Experiment (1985), was a wreck. Despite its bizarro premise of trying to replicate a "found" snuff tape, the film is little more than a misogynist demo reel for some rubbery gore effects, quickly abandoning its premise for overly flowering editing and shots that make you wonder why the killers seem to care so much for impossible camera setups. It was a rough start to the series, and to make matters worse, the sequels wouldn’t really be much better, often pinballing between being monotonously cruel or teeth-gratingly goofy.

The entries helmed by Hideshi Hino are the exception. Born in 1946, Hideshi Hino is, along with Junji Ito, Go Nagai, and Suehiro Maruo, one of the absolute masters of horror manga. From the very first publication of his serialized Hideshi Hino’s Shocking Theater in 1971, he carved out a unique niche with his mixture of almost adorably ugly character designs, surreal plots, and a level of ultraviolence and grotesqueries that would make even the most seasoned horror fans flinch. Predictably, when he got the chance to write and direct Guinea Pig, the results were nothing short of stomach-churning.

His first Guinea Pig film—and directorial debut—was 1985’s Guinea Pig: Flower of Flesh and Blood. With another faux-snuff premise front and center, Flower of Flesh and Blood feels a lot like course correction from The Devil’s Experiment. This time around, instead of focusing on a gang of sadistic killers out for gory entertainment, we follow "Samurai" (Hiroshi Tamura, and not, as legend claims, Hino himself), a gaunt man sporting white face paint and a black samurai helmet. Unlike the punks of the first film—or those of just about any empty "faux snuff" serial killer movie, for that matter—he’s a sculptor, a tortured (and quite pretentious) artist looking to carve his latest masterpiece.

The only catch is, he uses human bodies as a canvas. His latest base is simply credited as "Victim," a young woman played by Kirara Yûgao who we learn absolutely nothing about. The viewer’s gaze is the Samurai’s gaze as well, and he has no interest in who his captive is, what she does in life, or what she feels at any given moment. The film is not a narrative in the traditional sense, sporting no act structure, no character development, and no real character interaction beyond the Samurai giving empty pontifications on his artistic process to his bound and dazed captive. To quote Videodrome’s Max Renn, “It’s just torture and murder. No plot, no characters. Very, very realistic.”

However, that’s not to suggest Flower of Flesh and Blood doesn’t have a perverse artistry of its own. Unlike The Devil’s Experiment, which couldn’t seem to decide if it wanted to stick to found footage or go really abstract with its editing, Flower of Flesh and Blood feels cold, precise, calculated—less like gore sequences were slapped together and more like Hino took the time and effort to laser-focus in on shots and cuts that would make the audience the least comfortable and work from there. The camera lingers on shots of the Victim before harsh cuts whip the viewer to extreme close-ups of vivid dismemberment, often arriving out of synch with previously established editing rhythms. It all makes for a very claustrophobic and nauseating viewing experience, one that isn’t helped by the fact that it basically never leaves close-ups once the torture starts, only jumping back for wide shots to “admire” the Samurai’s work.

The disorienting rhythm of cuts and shots is one thing, but what they actually contain is a whole different ballgame. Despite its low budget, Flower of Flesh and Blood features some of the most genuinely upsetting and gut-wrenching gore out there, full of gushing dark blood and ripping latex skin. Rather infamously, when Charlie Sheen first saw the movie, he believed it to be an actual snuff tape, causing Hino to be investigated by the FBI before being cleared, putting him alongside Ruggero Deodato in the history books of shock auteurs put under investigation for their filmed bloodshed.

Needless to say, I don’t think it’s possible to really "enjoy' Flower of Flesh and Blood in any traditional sense—it’s not a film that’s looking for you to get any enjoyment. It’s less of a standard viewing experience and more of a challenge to be conquered, like Hino is staring you in the eye and daring you to watch the film from start to finish. As far as pure shock cinema goes, it’s probably the finest-crafted example out there, and a true testament to Hino’s skill as a terror maestro. I’m not sure if I can recommend it to most people—it’s the sort of film that makes you feel like you need a dozen showers by the time it’s over—but I can certainly say there’s nothing else quite like it.

After Flowers of Flesh and Blood, Guinea Pig wisely dropped the "faux snuff" angle, lampooning the concept with the ill-conceived He Never Dies before moving on to weirder, odder ideas (like hard sci-fi experimentation in Android of Notre Dame or goofy comedy with a drag queen in Devil Woman Doctor). Still, the series' ethos was the same—deliver high shocks for low budgets—and by the time Hino stepped behind the camera for the series’ sixth and final entry, Mermaid in a Manhole, it was practically unrecognizable from its first incarnations.

So Hino took this new freedom and made, by and far, the series’ finest hour. Directly adapted from one of Hino’s short manga, Guinea Pig: Mermaid in a Manhole is the story of Hayashi (Shigeru Saiki), an introverted painter whose works have taken on a darker tone after the recent loss of his wife. He spends his days in a haze, either cooped up painting in his cluttered apartment or visiting his "secret place": a polluted, trash-laden sewer built over a river he used to play in as a child, now full of discarded junk and filthy water.

One day, while lazing around in the sewer, Hayashi finds something new: a real, live mermaid (Mari Somei). Hayashi had seen her back in the river, but now, she has nowhere to go, trapped in a sea of junk, sick and miserable. But Hayashi, struck with a sudden burst of inspiration, takes her back to his apartment, and puts her in a bath of clean water, looking to take care of her while he works on his art.

Unlike Flower of Flesh and Blood, Mermaid in a Manhole isn’t some unrelenting assault on the senses. Instead, it’s a bizarre slow burn, taking its time to establish Hayashi’s daily routine, his connection with The Mermaid, and his cramped apartment space before letting loose with anything remotely horrific. In fact, I’d wager it isn’t even until a third of the way through the film that Mermaid in a Manhole starts to tip its hand that this is not, in fact, a proto-Del Toro tale of human/fish-person romance, but one of the nastiest bits of body horror to ever slither onto home video.

See, once Mermaid in a Manhole gets into its slow pace of the artist caring for The Mermaid, she begins to ooze. It turns out she’s decomposing. Pores on her body are bleeding in a variety of odd, pastel colors—pastel colors that would be perfect for a painting. The next thing you know, Hayashi is painting The Mermaid’s portrait with her own pus, hoping to whip up a masterpiece while trying to prevent her from withering away.

If you can’t tell already, Hino has a thing for the relationship between artists and their muses. It’s hardly subtle, sure, but the way Hino literalizes the destructive and toxic nature of artist/muse relationships through cruel bloodshed in Mermaid in a Manhole, Devil’s Experiment, and even some of his manga like the phenomenal Panorama of Hell packs a punch so blunt it’s impossible to ignore.

The idea of the destructive relationship gets even more literal in the latter half of the film, where once again, right when the audience adjusts to the new rhythm of just watching The Artist paint with the pus, things go straight to hell. As the painting develops, The Mermaid decomposes at a quicker speed, like a bloody reverse-Dorian Gray. And all of the sudden, the pacing changes, with all the slow buildup giving way to a non-stop visual vomitorium of flowing blood, splurting pus, and all sorts of worms, parasites, and leeches crawling out from under her skin—her body falling apart at the seams as Hayashi gets increasingly violent, aggressive, and horrified as he paints his opus.

While Flower of Flesh and Blood liked to capture the action in a direct, unflinching manner, Mermaid in a Manhole gets a bit more abstract with things. While still mostly going with all close-ups and medium shots for the body horror, the cuts are quicker and the lighting has a surreal, almost Bava-like green glow at times, abandoning any logic in favor of just delivering striking imagery. It’s a choice that adds a sort of fairy tale-like unreality to the already mythic plot, helping to make the weird tale all the weirder. Basically, by the time you’re watching forearm-sized leeches and a Black Magic 2-esque amount of worms crawl out from a mermaid’s boils and into metal buckets, it’s safe to say that reality can be thrown right out the window.

I know this might sound strange considering that it’s the sixth entry in an SOV gore series, but Guinea Pig: Mermaid in a Manhole really is a horror masterpiece. It’s just the right mix of slow burn, atmospheric horror and all-out gore mayhem, creating a pace and mood that is at once repulsive and impossibly hypnotic. Not only is it the best entry in the Guinea Pig series, I’m tempted to call it the best SOV film I’ve seen, and an absolute must-watch for those who have the stomach. Low-budget body horror rarely gets any better than this.

Next: Crypt of Curiosities: Shozin Fukui’s Cyberpunk Films