Gyo

Gyo is a Seinen horror manga by Junji Ito, also known for creating Uzumaki and The Enigma of Amigara Fault (which, incidentally, is an extra story in the back of the second volume).

During World War II, the Imperial Japanese Army commissioned a secret experiment to create biological weapons. The end result - a deadly bacteria that infected corpses and released nauseous gases, and a walking mechanism fueled by these gases, for the purpose of spreading infection. This plan was averted when the ship carrying the bio-weapon was sunk by American bombers during the war - but the bio-weapon remains active, infecting the sea life and spreading back into Japan in the form of undead walking fish...

It gets worse.

An animated OVA for the story was greenlit on March 2nd by ufotable. It seems that there are some artistic liberties with the OVA story such as Kaori becoming the protagonist as well as new side characters to boot. Whether this makes it a better adaptation or a poor rendition of Gyo is yet to be seen.

Trailer for the OVA can be viewed here.

Gyo contains examples of:

 * Alien Sky: A grey, swirling sky is shown off throughout the OVA. It's actually pretty by the end.
 * And I Must Scream
 * Bland Name Product: In the OVA, Tsuyoshi uses a BloodBerry.
 * Bloodier and Gorier: The manga had very little blood; the OVA looks like it's going to have gallons.
 * Blood Splattered Innocents: At one point in the OVA, Kaori slips and falls in a large puddle of blood.
 * Body Horror: A particularly gruesome moment when It was sad.
 * Brick Joke: The first walking fish is smashed and bagged,
 * Cassandra Truth: The fact that Kaori even goes into full-blown fits over a smell only she can smell didn't help.
 * Circus of Fear
 * Creepy Uncle: Tadashi's uncle, also a Mad Scientist.
 * Depopulation Bomb
 * Editorial Synaesthesia: Stink lines.
 * Everythings Even Worse With Sharks: The walking fish are initially a minor annoyance at the most - cue the literal land shark. When the stakes are raised with a freaking whale walking out of the ocean, it collapses under its own weight.
 * Everybodys Dead Dave:
 * Evil Hand: One of the legged machines is removed from the fish it was fused to, after which it latches onto a scientist's arm. Though he promptly amputates it it starts crawling around for a while.
 * Evil Smells Bad: Basically what the story is about.
 * Evil Uncle: More like callous and really crazy uncle.
 * Fate Worse Than Death: Ignoring the physical Body Horror for a bit, the bacteria slowly paralyses the victims' muscular and nervous systems, keeping them vegetative but very much alive.
 * Final Girl:
 * Fog of Doom
 * For Science
 * Hot Scientist: Ms. Yoshiyama
 * It Got Worse: See the cover of the first volume up there? With the zombie fish? Here's
 * Karmic Death: The soldier who shoots at
 * Madness Mantra: Aki chants "Die, die, die, die" under her breath as she simmers over Kaori leaving and Erika engaging in a threesome.
 * Mad Scientist
 * Monumental Damage: The world's doom is sealed with a montage of swarms at the Eiffel Tower, Taj Mahal, Empire State Building, and Kremlin.
 * Ninja Pirate Zombie Robot: Zombie fish. With robot legs..
 * Raising the Steaks
 * Scenery Gorn
 * Screaming Woman: Kaori. In nearly every scene. In the anime, however, she is noticeably much calmer.
 * Spared By the Adaptation: in the anime.
 * Spider Tank: All the walking fish are really fused with these. They steadily get bigger to carry bigger bodies...
 * Take Our Word for It: It's a good thing that there's no media that could express the monsters' smell to us. Though they keep saying that it smells like death, which anyone who's ever had to deal with gangrene knows all too well. (Or if you work in a morgue).
 * A Threesome Is Manly: Erika and her two strangers.
 * Time Skip: Invoked when the hero tries to seek help but falls into a canal and goes into a coma for a month.
 * Unreliable Narrator: Erika and her gentleman friends are less than truthful in their television interviews.
 * A Threesome Is Manly: Erika and her two strangers.
 * Time Skip: Invoked when the hero tries to seek help but falls into a canal and goes into a coma for a month.
 * Unreliable Narrator: Erika and her gentleman friends are less than truthful in their television interviews.

GASHUNK