The plot of Gyo centers around the "death stench", a revolting smell first encountered in connection with creatures appearing to be bizarre fish with scuttling, sharp metal legs. At first they appear merely as smaller fish, but later also as larger sea creatures such as sharks and even a whale.
The creatures are eventually revealed to consist of a small metallic, legged structure with the carcass of a dead animal (and later, human) strapped on top. Germs infecting the rotting body produce a gas - responsible for the terrible smell that surrounds the creatures - that makes the metal construct move.
Later, it is found that the Japanese Army was researching germs that produce the death stench during World War II in a desperate effort to turn the tide of the war. Infection by the germ produced large amounts of foul-smelling gas from body tissue, and since infection quickly killed the test animals, walking machines were built to carry them further, allowing them to reach and sicken enemy troops. Enemy planes sunk the ship carrying the prototypes for the walking machines, which ran entirely on the gas.
Underwater the machines have attached themselves to the fish and moved from the island to the mainland, attacking the humans. Later it is found that the death stench gas might have a will of its own, and that the machines are not man-made: the disease has apparently mutated to be able to construct the walkers from the metal hulls of sunken battleships.
Main character of Gyo. In the beginning it shows that he loves scuba. He has a girlfriend named Kaori and an uncle named Koyanagi. He noticed something was funny when Kaori said he had bad breath, although he brushes his teeth twice a day. He tries to save Kaori but in the end he fails to do so. He is trying to help with the fight against the creatures. At the end he joins a group of university students, who happen to be immune from the death stench, to create a vaccine to defeat the disease. He's the only survivor of the main characters and appears to be immune.
Tadashi's girlfriend. She has an extremely sensitive nose and becomes very jealous when Tadashi is near other women. Near the beginning of the series Kaori started noticing the odd smell. She and Tadashi tried to escape and went to Koyanagi's lab. Due to her overly sensitive nose, she seems to be able to sense when the creatures are coming. However, she is later infected, causing her body to swell up and be covered in boils. The germ also forces the gas with the "death stench" out of her body. Because of this, she began to think she was disgusting, that Tadashi wouldn't love her if she wasn't beautiful, and she would never be healed. This, along with the horrible stench, made her hang herself from the wires of a ceiling lamp. But the wires were weak and could not support her additional weight with the gas bloating her. Tadashi then immediately carries her to his uncle Koyanagi's lab for aid. It turns out Koyanagi rigs her up to a custom walking machine. Ultimately, she becomes like the walking dead creatures, except for one quality - she has a will of her own. Later she was captured by the Citrous Circus, whose ringmaster was using the infected creatures and humans along with the gas, as attractions. Kaori escaped and fled. Tadashi dragged her back to Uncle Koyanagi's lab. But when she escaped outside again after thinking Tadashi was now attracted to Ms. Yoshiyama, she was attacked by the other creatures. It is likely that this was because they saw her man-made walking machine as a threat to their existence. Near the end of the series, Tadashi finds her burnt corpse, commenting on how she is 'finally rid of the smell'.
Uncle of Tadashi, an inventor and has an assistant, Ms. Yoshiyama. He tries to figure out what makes the fish move. He once smelled a human corpse, relating the stench to the stench of the creatures. It was his father who died of a heart attack in a factory during a hot summer. While dissecting the fish he notices that although the fish is dead the walker's legs still function. When he got too close, the legs then clamped onto him. He cut off his arm to prevent the infection from spreading to the rest of his body. He is fascinated by the machine, not caring that he lost an arm to it. He gets stabbed by Kaori's spider-like leg and dies. He puts himself on a flying version of the mechanical legs and tried to kill Tadashi and Yoshiyama, presumably because he assumed that Tadashi and Ms. Yoshiyama had become partners, but failed. Outside he waited for them to leave the building, and took Yoshiyama with him before flying away. He is last seen as the Citrous circus and other walking machines attempt to bring him down by gas cannon, only for his own machine to extend metallic wings and escape.
Assistant of Doctor Koyanagi, she cares for him and tries to help him. When she was seen with Tadashi by Kaori, Kaori tried to attack her. Ms. Yoshiyama then ran outside where she was captured by the Mechanical Koyanagi. Her final fate is never revealed.
"The Sad Tale of the Principal Post" is the twentieth chapter of the manga "Gyo". The short story starts off as a group of family and friends celebrate the completion of a family's new home. Once the celebration is underway, the daughter of the man who built the house is alarmed when she hears cries for help emanating from somewhere in the house. She quickly announces, "that sounds like dad!". At once the guests and family members proceed in search of the source of the cries for help. After realizing they are emanating from the crawlspace in the basement, they head downstairs. When they get there, they are astonished to find the father pinned beneath the principal post of the house. Somehow, under precarious circumstances, he found himself trapped with the whole weight of the house crushing him. The daughter suggests calling a carpenter, but the father is reluctant to accept help in removing himself, fearing the structure would entirely collapse. He doesn't want to see the new home for his family, which they adore, destroyed by removing him. His final decision is to be left there since he is going to die anyway. Later in the evening, he dies while the friends and family watch over him. In the end the house remains intact due to the efforts of the father. A shrine is kept by the principal post in honor of his final brave act to save the house.
List of Chapters
|1.) The Death-Stench of the South Seas|
|2.) The Death-Stench in the Air|
|3.) Going Ashore|
|4.) Shark Attack|
|6.) The Death-Stench Creeps|
|9.) The Death-Stench invaders, Part1|
|10.)The Death-Stench invaders, Part 2|
|11.) Pale Kaori|
|12.) The Death-Stench Device|
|13.) The Inheritors|
|14.) The Pull of the Death-Stench|
|15.) The Death-Stench Circus, Part 1|
|16.) The Death-Stench Circus, Part 2|
|17.) The Death-Stench of Lab #2|
|18.) The Death-Stench Air Raid|
|19.) The Death-Stench World|
|B1-The Sad Tale of the Principal Post|
|B2-The Enigma of Amigara Fault|