The Gedoushu are malevolent spirits living in a giant Chinese sailing ship (Rokumon Junk) that sails along the Sanzu River. Able to squirm their way into the world of the living, they attack humans so that the river overflows and flood the mortal realm. Though defeated and sealed by samurai eighteen generations ago, the Gedoushu reawaken in present time to resume their havoc.
Chimatsuri Doukoku is the leader of the Gedoushu. He is armed with a broadsword and possessing the power to seal his fellow Gedoushu. He battled the Shiba Clan's previous Shinkengers, and had been sealed by a former holder of the title Shinken Red before he died. Because the seal was incomplete, Doukoku eventually revives and begins leading his forces in conquering the mortal realm by terrorizing humans in anyway possible so that the river overflows to point of flooding into the mortal realm in order for them to invade in full fury. He is in a constant state of rage that only sake and Dayu's music can control.
Learning of the seal placed on him, Doukoku briefly changes his plans to target Takeru as the death of the Shiba Clan would ensure that he would never be sealed again. But when that plan failed, Doukoku has his force carry on the original plan without giving wind of this knowledge to any Ayakashi with his own agenda. During the summer while in a comatose state that leaves him open to his enemies, Doukoku manages to suppress his magnified power and transfers it to Gozunagumo. Later, after learning of Akamaro's true intentions, Doukoku risks his life to enter the mortal realm to repair Dayu's shamisen.
As a result, he has to be submerged in the Sanzu River to rehydrate. But after the Shiba Clan real 18th head is revealed, Dayu uses Shinza's anguish to bring Doukoku back to the mortal realm. After absorbing Dayu's energy to heal his body, Doukoku overpowers the Shinkengers and brings the Rokumon Junk into the mortal realm and the Sanzu River floods the city. Dayu's energy covers him with a protective layer that reduces the effects and damage of the Sealing Character to practically nothing.
Thinking he had broken the Shinkengers' spirits when they attempt to defeat him, Doukoku is immobilized before Shinken Blue delivers the final blow. Assuming his second life, Doukoku overpowers Samuraihaoh before being finally destroyed by Shinkenoh as he attempts to take the Shinkengers down with him.
Usukawa Dayu is the right hand of Doukoku and the only one he is kind to, provided she knows her place as his obedient and unquestioning servant. In life, she was Usuyuki, a woman who obsessed over Shinza, a man who never loved her. However, when scorned that he loved another woman instead of her, Usuyuki incinerated him and those at an engagement party in a suicidal crime of passion. But once witnessing that Shinza would still love another, Usuyuki's emotions corrupted her soul and turn her into Dayu, bonding Shinza's soul into a shamisen that she carries with her, creating eerie and unsettling songs that become a means to soothe Doukoku's rage.
However, she has trouble getting along with the Ayakashi because of her life as a human, which she makes attempts to reclaim. One failed attempt results with her being saved by Juuzo, developing feelings for the Gedou as she begins to defy Doukoku's orders as well. Though she claimed her feelings for Shinza had long died, after becoming a rogue, Dayu refuses to give him up as it would end her existence and she doesn't want Shiza's soul to be reunited with his love. Doukoku angry that she did not killed Juzo as he ordered her to, he burnt her shamisen, making Shinza moan. She told Juzo her feelings for Shinza had disappeared but Juzo did not believe this true.
Soon after Akumaro's demise, Dayu returns to the Rokumon Junk to assist in Doukoku's reawakening. Dayu deliberately has Shinken Pink destroy her shamisen. Which discards her of her past life, but it also revives Doukoku. She later uses the last of her power to restore Doukoku's body with only her kimono remaining, which Doukoku later throws into the Sanzu River. In battle, Dayu wields a shortsword hidden in her shamisen, with the headstock as its hilt. Her name is translated as thin-skinned courtesan and she is the basis for the futakuchi-onna of Japanese myth.
Bony Shitari is the strategist of the group, a squid-headed demon who awaited for Doukoku's revival. He sees humans as mere pawns for his research, attempting to find ways in order to overflow the Sanzu River. He also stole texts from the Shiba Clan which he used to learn about the seal placed on Doukoku. Though he warns Doukoku not to trouble himself with the Shiba Clan's sealing character so not to attract attention from certain Ayakashi, Shitari recruits Isagitsune in an attempt to quench his curiosity on what the sealing character is. He later recruits Oinogare in an attempt to re-open a well the Gedoshu used in the past as their portal by sacrificing nine maidens, formally introducing himself to the Shinkengers as a result.
During the events of Kamen Rider Decade episodes 24 and 25, Shitari witnesses Daiki Kaito stealing the Ika Origami and sends the Ayakashi Chinomanako to investigate the otherworldly Kamen Rider Diend, causing the chain of events that would doom their world. Fearing Doukoku's power, Shitari ended up helping Gozanagumo, by poisoning Takeru and propositioning him to give him the seal in exchange for the antidote. When Doukoku reawakens, he returned to his good graces. He also kept the secret that Dayu had feelings for Juzo from Doukoku and defended her when he grew angry that she didn't kill Juzo when he asked her to do so.
When Akumaro arrives, Shitari expresses a great deal of distrust over the mysterious Gedoushu and not as much shocked when his impression of him was accurate yet was powerless to do anything against him as he realized Akumaro's intentions. After Dayu returns, Shitari decides to kill off Takeru, only to learn the truth behind him and the Shiba House's true leader and giving up half of his life in an attempt to speed up Doukoku's reawakening. He remains on the Rokumon Junk during Doukoku's final battle with the Shinkengers, going down with the ship as it sinks in response to its master's death while proclaiming that he cannot die.
The Nanashi are the foot soldiers armed with swords and bows that serve the Gedoushu. The Onanashi Company is a subgroup of Nanashi, who are naturally born giant. They slither from between buildings to fight the Shinkenger. The Ozora Nanashi Company are naturally born giant with a flying variation.
Appearing in the Shinkenger movie are the Kusare Nanashi Company, and the Kusare Onanashi Company, who resemble normal Nanashi and Onanashi but in red garbed attire.
Juzo Fuwa is a mysterious Gedoushu, regarded by the others as a lone wolf, yet he seems to know more than Doukoku about the Sanzu River's true potential. He first appears in Episode 7. Juzo was previously a human master swordsman in life, eventually becoming disenchanted with the ways of bushido and thriving more on the pleasure of killing his opponents in battle. When he contracts a fatal illness, Juzo enters the Sanzu River to cheat death, completely discarding the goodness in his heart to become a Gedou, a half-Gedoushu that can freely exist in both realms and keep his human form. As a result, Juzo is condemned with an insatiable urge to find an ideal opponent, a fellow samurai who strays from the teachings of bushido, to clash blades with, saying his katana, Uramasa hungers for it.
He finds this opponent in Takeru Shiba, after witnessing his swordfighting. He had asked Doukoku permission to fight Shinken Red and Doukoku blindly approved without realizing he was the one to seal him. This obsession with fighting Shinken Red leads Doukoku to seal Juuzo's Gedoushu powers, leaving him for dead in the Sanzu River. Although he barely survives with Dayu's aid, he cured Takeru of Shitari's poisoning. He makes Takeru promise to fight, but when Gold comes to save him, Juzo agrees to fight the next time. After a long battle in which he manages to severely wound Shinken Red, Juzo is defeated and falls off the cliff into the ocean below in Episode 26. Dayu seemed to have feelings for Juzo but after he made her realized she hadn't given up on her feelings for Shinza, she was peaved at him.
Later fed up waiting for the Uramasa to be repaired, Juzo confronts Akumaro and learns his weapon's origins and that he is a pawn in his plan. by fooling Akumaro into giving him back his tool and cutting him down, Juzo reveals he knew the truth behind Uramasa from the first time he held it, thus preventing Akumaro from fulfilling his plan. Later, after the real Shiba House head is revealed, Juzo gets Takeru to duel him once again before finally falling to him in battle with a delayed hit after Uramasa finally stops its master and denies him his only desire. Uramasa remains in the physical world after Juzo fades away until the souls that formed it are finally able to depart into the afterlife.
The Susukodama are a furred ball-like soot settling in roof of the Rokumon Junk's interior, appearing whenver Doukoku's infuriated enough for them to descend, annoyingly repeating people's words while giggling. Kodoma are spirits believed to live in certain tree, cutting down a tree housing these spirits is thought to bring misfortune. They are similar to the Dryad of Greek myth.
The Sakamata are monsters within the Sanzu River that are more powerful than the Nanashi Company. The Sakamata resemble tremendous, skull-like, eyeless, crocodilian heads on two legs, and can breath fireballs quite readily. There are also some Sakamata known as the Onosakamata, which are naturally born giant, they appear in Episodes 23-25, they are a pale gold color. Appearing in the Shinkenger movie are the blue-skinned Kusareno Sakamata and Kusare Onosakamata (left).
Akumaro Sujigarano first appears in Episode 27. He is a Gedoushu general with six slitted eyes and rictus grin, appearently stronger than Doukoku. A master of the black arts, Akumaro can create monsters called Kirigami by performing an act also known as kirigami. He also uses his fan and iron claw hands as weapons.
Emerging from the bottom of the Sanzu River, Akumaro offers his aid to Doukoku, who leaves him with what would later become a weak spot in his left shoulder region. Akumaro starts setting up markers and recruits Juzo and Dayu into his service to make use of them. Eventually found out to be using Doukoku for his own agenda, Akumaro falls back after Doukoku nearly destroys him.
However, with Doukoku resting, Akumaro takes over the Rokumon Junk as he completes the final marker to open up Hell and finishing Uramasa's repairs. Akumaro is left with nothing when he realizes Juzo can not complete the Urami Gandogaeshi and goes into an enraged fury and his first life is taken by the Shinkengers' Rekka Daizantou and Super Mougyu Bazooka. After becoming a giant, Akumaro is defeated by the Shinkenger and he laughs because his desire has been granted.
Manpuku Aburame is the main antagonist in Samurai Sentai Shinkenger The Movie: The Fateful War, the leader of the Kusare Gedoushu, a group of powerful Gedoushu who were sealed away three centuries ago by Restudo Shiba. However, he is revived by Doukoku along with his followers. He is destroyed by Kyoryu Shinken-Oh.