Ashu Clan
The tribe are a race of demons who were sealed away in the World of Demons by the Takaoka Clan who used the Mirror of Demons. BoukenSilver has been fighting these unleashed demons for a while as he has been fighting the Negative Syndicate for years.

Gai
Nickname: The Fierce Devil
EPISODE 17-19
Height: 209cm to 44.5m
Weight: 92.5kg to150t
The leader of the Ashu Tribe, a purple and green demon who has a bazooka. He and BoukenSilver are bitter rivals. With Hyouga, Gai kidnapped Natsuki and used her blood to free Rei from the 100-Demon Mirror. With Rei's assistance he disguised himself as Satoru's old companion Masaki to confuse and kill him with the precious Fighter's Crossbow. The illusion disappeared when Satoru confronted it. Gai personally killed Eiji's father in front of him after revealing his half Ashu orgin. Eiji threw his monk staff at Gai defeating him and was terminated by Ultimate DaiBouken and the Ashu Spirit Extinguishing to later be revived by Gajya.

Hyouga
EPISODE 17
Height: 205cm to 55.0m
Weight: 92.5kg to 150t
Was the first the other Boukengers faced. His colors are blue and blackand has an icy crown-like horn that excreets lightning pulses. With Gai, he kidnapped Natsuki. He defended Gai. He was the first to fight the other Boukengers and was defeated by the Dual Crusher Drill Head (wielded by BoukenRed) when trying to protect Gai and physically destroyed by Ultimate DaiBouken after giving a thrashing to Super DaiBouken, but his spirit was completely extinguished off with the Ashu Spirit Extinguishing.

Rei
Nicknamed: The Great Beast
EPISODE 17-19
Height: 207cm to 46.5m
Weight: 93.4kg to150t
Gai and Hyouga freed this powerful tiger-like demon from the 100-Demon Mirror by using Natsuki's blood. He appears to be superior to Gai, as even Gai refers to him as "master". He has power over fire. He cast an illusion inducing mist on Gai making Satoru think that he was his old partner Masaki, while Gai shot him with the Fighter's Crossbow, however Satoru eventually saw through the deception. Defeated by Satoru wielding the Crossbow of Fighters, and terminated by Ultimate DaiBouken and the Ashu Spirit Extinguishing..

Quester Gai
Height: 220cm
Weight: 128.8kg
First Appearance: 20
Last Appearance: 42
Only to be revived by Gajya's Gordom Engine as Quester Gai. In this form Gai wields two guns that also act as short swords, as well as the ability to create energy waves with the Gordom Engine. Eiji relentlessly went after the Questers and their plans until he seemingly defeated him in Episode 42.

Quester Rei
Height: 218cm
Weight: 133.6kg
First Appearance: 20
Last Appearance: 42
Only to be revived by Gajya's Gordom Engine as Quester Rei. In this form Rei wields a sword that also acts as a gun, as well as being able to create energy waves with the Gordom Engine. He got all the members of the Negative Syndicate to get various Precious in Episode 41 to put inside the Mercurius Veseel, which did not make any concerning group happy. He is also the one that put Natsuki under a trance in thinking she must destroy the world in Episode 33. Eiji relentlessly went after the Questers and their plans until he seemingly defeated him in Episode 42.

Quester Robo Turbo (Rapidly)
Height: 53.0m
Weight: 1250t
EPISODE 21
Built by Gai and Rei for their plan to steal a Precious from a building. It was the first Quester Robo, techincally the last one they piloted was a Gaiya God. It almost defeated the Boukenger but luckily Souta's ex-partner Toba planted a bomb in the Robo and qeaken it enough to be destroyed by Siren Builder's Triple Liquid Bomber and Ultimate Daibouken's Ultimate Buster.

Quester Robo Elite (Commander)
Height: 46.5m to 52.0m
Weight: 1268t to 1560 t
EPISODE 28
Designed specifically for it to use the precious "The Legendary Armor". In the first battle with this Robo, Ultimate Daibouken couldn't defeat it with it's twin arm cannons and 6-missile launcher. When it finallt wore "The Legendary Armor" it was stronger and impervious to any attack. Masumi's idea to persist caused overheating to the robot. The Boukenger succeeded in retrieving the armor and destroy it with a combination attack.

Quester Robo Blaze (Erupt)
Height: 50.0m
Weight: 1450t
EPISODE 31
It is based on a battle chopper and performs airborne attacks. Designed to use "The Fire of the Ruined Country" as it has a special chamber in it's head to place it, with it, and through the turbines on his shoulders, this Quester Robo uses a extremely powerful flame thrower that can nearly melt even Ultimate Daibouken's armor. Was destroyed by Ultimate Daibouken's Ultimate Blaster courtesy to Sakura's short-range attack.

Quester Robo Radial (Advance)
Height: 65.0m
Weight: 1550t
EPISODE 36
Designed after an armored tank. It can generate electrical power with it's Gordom Engine. Created to use the Precious "The Mountain Crushing Iron Rod" and cause havoc with it. In a test run, it could only destroy a single mountain but in the completed form using the Precious, it was stronger than the Siren Builder and Dai Voyager put together. It was destroyed when the mysterious boy Taro took back the Precious with his bare hand and gave the chance for the Boukenger to use the Triple Liquid Bomber and the Adventure Double Screw.

Quester Robo Cannon
Boukenger the Movie
Designed after a camouflaged tank, the Questers used it to go after the Precious all the members of the Negative Syndicate wanted. Eiji combated them with the SirenBuilder and ultimately destroyed the robot.

Ouga
Height: 216cm to 62.0m
Weight: 103.3kg to 166t
The chief of the Western Ashu tribe was sealed long ago. When the Boukenger first meet him, he is in a forest that is completely dead. He aims to killed Eiji because his mother, Kei was from his same tribe (and he knew her since he was little) and her soul cannot complete it's travel to the other world with Eiji still alive. Eiji performs the Ashu Soul Vanishing, but Ouga who is defeated as a giant, with his very last bit of strength, takes Eiji's soul with him, leaving nothing but a petrified body. Ouga's Ashu soul is an "Absorbing Soul" which allows him to absorb life from surrounding life forms to heal his wounds. He uses "Hundred Demons Heat Haze Reflection" to create copies of the Boukenger and attack them.

Homonculus Quester Jet Over (Scramble)
Height: 19.5m
Weight: 450t
EPISODE 41-2
The Homonculus was created by three Precious (Wize Men's Herb, Caduceus Staff, and Paracelsus' Mercury) mixed in the Mercurius Vessel and the Quester's jet was put over it to make an armor. After they seemingly defeat the DaiVoyager and injure the Boukenger, they bashed in the rest of the Negative Syndicate.