Whilst investigating the urban legends of the Undead, Kotaro Shirai stumbles upon the two Kamen Riders of BOARD.

BOARD is in pieces. Left reeling by Tachibana's betrayal, Kenzaki is forced to respond to another Undead attack.

Hirose manages to get access to Chief Karasuma's hard drive. While they search to find him, another Undead attack brings Tachibana back to the frontlines.

Tachibana reveals the truth behind the BOARD attack, and warns Kenzaki that the Rider System will destroy his body.

Hearing an urban legend about a cave where you can hear the voices of the dead, Amane drags Kotaro and Kenzaki along. However, the Centipede Undead attacks...

Kenzaki discovers the link between Amane and Chalice. An enigmatic man appears with the goal of capturing the Rider System users.

Kenzaki is captured by the mysterious Isaka, but Tachibana manages to escape the attack. He enlists help from Shiori and Kotaro to search for Kenzaki.

Kenzaki and Karasuma carry an injured Tachibana as they narrowly escape Isaka’s facility. Karasuma reveals the truth about Isaka and his organization.

While Tachibana questions his ability to become Garren and fight the Undead, Hajime struggles to understand his humanity.

Tachibana's "sickness" is cured and he is able to transform into Garren once again, but at what cost? Hajime questions Jin on human emotions.

While fighting Ikasa, the Peacock Undead, Blade is attacked by an unlikely opponent - Garren. Meanwhile with no place else to go, Hajime stays with Jin, but an Undead appears.

It's Blade vs Garren as the Spider Undead—a more powerful, Category Ace Undead—appears. A worried Sayoko investigates the cause of the changes in Tachibana’s body.

Isaka's plans are in motion, as he seeks those marked by the Spider Undead - those with the potential to become his perfect Rider.

As the race to seal the Category Ace continues, Ikasa sets his sights on the one thing that could interfere with Garren.

The Dragonfly Undead kidnaps Amane and her mother, intending to lure Hajime into a trap. Isaka's Rider System is complete, and all that remains is finding a compatible host.

Tachibana retires as Garren, after his involvement in the creation of Isaka's Rider System. That night, the Leangle belt goes missing.

Leangle has found a host, and within minutes reveals a dangerous new ability. Who has succumbed to the power of the evil belt?

Leangle attacks and overwhelms Kenzaki while Kiryu from BOARD reprimands Tachibana for leaving the battle.

Kiryu steals the Leangle buckle and transforms. Drunk with power, he attacks. His fate and Mutsuki’s are now twisted due to their newfound obsession.

Something sinister grows within Mutsuki after he recovers the Leangle belt. Kotaro, still distrustful of Hajime, becomes entangled in an Undead plot.

Tachibana and Mutsuki arrive as Chalice seals the Undead. As Chalice fights Garren, Leangle takes control of Mutsuki again, but the fight ends quickly. After fighting the Capricorn Undead, Kenzaki brings Shirai back home. Tachibana decides to train Mustuki so he can control the belt and Tachibana learns about Mutsuki's nightmares. The Orchid Undead traps Shirai and the Capricorn Undead fights Kenzaki without his belt. Chalice frees Shirai and the Orchid Undead flees. Blade then seals the Capricorn Undead.

Tachibana continues to train Mutsuki to overcome the Spider Undead. A friend of the Kurihara family, Kamioka, takes Aikawa on a photo shoot. Garren and Leangle try to seal the Mole Undead, but Mutsuki loses control again and is dragged underground. While on the job at the zoo, Aikawa is attacked by the Orchid Undead. The Eagle Undead arrives and drives the Orchid Undead away. While Mutsuki tries to find a reason to face and seal the Undead, Blade and Garren become overwhelmed by the Mole Undead.

Mutsuki overcomes his fear and seals the Mole Undead. Kamioka begins questioning Aikawa's presence at the Kurihara house. The Eagle Undead kidnaps her to trap Aikawa and steals his Change Card. Blade arrives and sees Aikawa transform into the Dragonfly Undead. The Orchid Undead attacks Mutsuki but flees. Blade retrieves Aikawa's Change Card from the Eagle Undead and seals him. Kamioka discovers Aikawa's secret but now believes in his goodness.

The Wolf Undead is changing people into werewolves. While fighting them at an amusement park, Leangle meets a group of human Undead Hunters. Leangle, Blade, and Garren encounter the Wolf, Orchid, and Elephant Undead, but they all escape. The Undead Hunters meet with Kenzaki and Garren to discuss an alliance. They help the Hunters complete a new bike, Black Fang.

The Wolf Undead steals Black Fang as Garren and Blade try to retrieve it. Chalice chases after the Orchid Undead, but Shirai finds her and heals her wound. Kenzaki and Tachibana find Shinmei, the leader of the Hunter, and discover that he is the Wolf Undead, so they chase him to the docks and seal him. Chalice finds the Orchid Undead and seals her.

The Elephant Undead arrives and defeats Blade and Garren. A strange man, Noboru Shima, shows up at Shirai's house with news from Karasuma. The Spider Undead begins to regain control of Mutsuki. The Elephant Undead seeks out Chalice and wounds him. Everyone learns that Shima is actually the Tarantula Undead, though he still wishes to help. While fighting the Elephant Undead, Shima gives Blade a Rouze Absorber, which transforms him into Jack form. He then seals the Undead.

Mutsuki begins to falls under the control of the Spider Undead again. The Buffalo Undead appears and Garren and Blade rush to seal it. Shima confronts Leangle about releasing Mutsuki, but the Spider Undead persists. After Tachibana is wounded by Mutsuki, Shima attempts to properly seal the Spider Undead in order to save Mutsuki. While on the way to stop Shima, Blade encounters the Buffalo Undead and seals it.

Leangle fights Shima, but Blade arrives to stop them. While Shima and the others think of a plan, Mutsuki continues to struggle against the Spider Undead. While trying to find Mutsuki, the Woodpecker Undead begins attacking people and Garren goes to seal it. Leangle and Shima meet again to fight. Blade arrives to stop them, but is unable to. Shima allows himself to be sealed by Leangle.

Azumi, the Serpent Undead, finds Aikawa and fights him with the help of the Tortoise Undead. Garren and Blade show up to help as Chalice staggers away. Having lost his memory, Aikawa encounters Ryo Mikami, a takoyaki vendor that looks like him. After the vendor shakes off his initial shock, Mikami proposes that the two trade identities in order to avoid a life he feels is too difficult. Posing as Aikawa, Mikami is found by Amane and taken back to Kenzaki and the others. Meanwhile, Aikawa begins to blend into Mikami's life.

The Serpent Undead continues to search for Aikawa. Mikami learns about Aikawa's identity, and tries to get his life back. Mikami's girlfriend, Michi, learns the truth about Mikami and Aikawa, but is happier with Aikawa. Michi and Mikami's fathers have a vendor contest which is interrupted by the Serpent Undead. Aikawa regains his memory and seals her. The Tortoise Undead intercepts Blade and Garren on their way to the battle. Aikawa arrives and gives Garren the Queen card. Garren then transforms into Jack form and seals the Undead.

While terrorizing people, Leangle is photographed by King, the Caucasus Undead in human guise. Kenzaki asks Aikawa to join them, but Tachibana does not trust him. King creates a website to slander the Kamen Riders and everyone seeks him out. Kenzaki encounters King, but has his Blay Buckle stolen by the Scarab Undead, who can stop time. Tachibana finds Mutsuki in a bar and learns of Aikawa true identity as the Joker Undead. Kenzaki retrieves his Blay Buckle, but Aikawa is abducted by the two other Undead. Kenzaki then encounters Trial D, an Undead that cannot be sealed.

Garren arrives to assist Blade and drives off the new Undead. Tachibana tells everyone about Aikawa's identity as the Joker Undead. Meanwhile, King holds Aikawa and forces him to transform into his Joker form, which he uses to escape. Tachibana meets Hirose's father, who is behind the Trials. Kenzaki finds Aikawa and learns about how he changed from the Joker Undead to Hajime Aikawa. King and the Scarab Undead appear and fight Blade. Aikawa helps Blade seal the Scarab Undead while King flees.

Blade and Garren fight over what should be done about Aikawa. Hirose's father contacts Tachibana and shows him the Trials. The Kenzaki encounters King and learns that Aikawa needs his cards to prevent his transformation into Joker form. Kenzaki is defeated and later ambushed by Trial D.

Kenzaki realised what was Trial D's motive. He decided to leave town to avoid further harm to other people. Mutsuki battled Hajime into a battle but was attacked by his Fusion Wolf form instead. King also gave Mutsuki Chalice's cards. King was surprised that his popularity grew but was interfered by Blade instead. Blade finally sealed his final deck card, Evolution Caucasus. He also managed to fuse into King Form and destroyed Trial D with Royal Straight Flush.

Another Trial Undead is hot on Kenzaki's trail, he can also use Kenzaki's moves! Meanwhile, Hajime can no longer control himself and fights assuming his Joker form.

Hajime has been taken over by his Joker form. No longer in control of himself, he cannot see the differences from humans and Undead and it's Kenzaki's King form to blame.

In order to get back Hajime from his Joker form, Kenzaki asks Mutsuki to give him the 5 cards of the Chalice deck that are in Mutsuki's hands, but for that he must let Mutsuki have his Rouze Absorber. Kenzaki makes the deal and with Tachibana, obtains the King of Hearts card. Hajime uses the card to finally suppress the Joker form and defeat the Trial.

Hajime's problem was solved as he can turn back into a human, but the new problem is on Kenzaki as he and Mutsuki have been tricked by Hirose to fight each other, and Leangle forces Blade to change into King Form. But he knows the King Form is fighting like crazy, but then Chalice comes with the Wild Form and suppresses the power of Blade's King Form.

Yoshido captures Mutsuki to create a new trial named Trial G, based on his Rider data. Meanwhile, Blade was followed by a new Trial, without knowing that it is Yoshito in disguise.

Hirose uses herself as bait to meet Yoshito (Trial B) so that the Riders can destroy him. Unfortunately, Trial G interfered and they have to stop him before it targets Hirose.

Mutsuki wishes that he will be the strongest Rider by fighting against the Tiger Undead but loses instead. But while confronting the Giraffa Undead, the Tiger Undead learns the truth behind the "Battle Fight" before facing Tennoji and his creation: The Titan.

After being poisoned by the venom of the Scorpion Undead, one of the two Undead fused into the Titan. Mutsuki attacks his friends and turns into the Category Ace. Everyone is not spared even his girlfriend, Nozomi. The Tiger Undead has already been sealed and Mutsuki is forcing himself to fight Blade in his King Form. Will the transformation be complete or a failure?

Using the abilities of the Chameleon Undead, the Titan tricks the Riders into fighting each other.

All the Riders get together to fight the Titan, and Blade's King form finds a new attack combo, the Four Card.

New Undead are born, and its identified as a fifth ace Keroberos, now all 4 Riders must face this powerful new Undead.

Though Keroberos was sealed, Tennoji reveals his true plan as he fuses with the sealed Undead to become all powerful. However, once Tennoji is defeated, the Giraffa Undead murders him and takes the Keroberos card, allowing the true Battle Fight to begin.

There are only two Undead left and if it's up to Garren, the Joker goes first, but in the heat of battle, will he change his mind or die trying?

With Garren out of the game and Hajime declared the winner, Blade and Leangle are the world's last hope, to seal the Joker. However, they have to deal with the endless army of Dark Roaches that are systematically destroying the human race.