Hojo Emu, an aspiring doctor, decided to join Cyber Rescue Center as an intern after discovering his Bugster-fighting abilities as Kamen Rider Ex-Aid.
Now a member of the CR, Emu is introduced to his co-worker Hiiro Kagami, also known as Kamen Rider Brave, but Emu's disapproval of Hiiro's attitude towards the patients lead them to get hostile toward each other.
Emu follows a patient who's fled in fear of a doctor and encounters Taiga, who transforms into Kamen Rider Snipe. Once Emu learns of the past connection Taiga had to CR, he visits the dark hospital Taiga resides in to rescue the patient.
A new patient appears, but Emu is unable to provide assistance after he lost his Mighty Action X Gashat to Taiga. However, Kiriya Kujô, also known as Kamen Rider Lazer, approaches Emu and offers him a chance to recover his Gashat in exchange for his help.
When a dangerous criminal is infected with the Bugster virus, Emu and Hiiro clash about saving his life or not, and the identity of the mysterious Kamen Rider that is attacking the others is finally revealed.
Kuroto Dan, or rather Kamen Rider Genm, swears to get back on Emu after being defeated by him in their last clash. Meanwhile, more details are revealed regarding Taiga's feud with Hiiro, and the reason why Taiga is eager to get revenge on the Graphite Bugster.
Kiriya tries to warn Emu and co. that Kuroto is the one behind the mask of Black Ex-Aid. However, upon Black Ex-Aid's defeat, it was someone else that takes the position.
Taiga Hanaya/Kamen Rider Snipe manages to destroy the Bugster which escaped in the last episode, and obtains the Jet Combat Gashat.
Graphite infects the Minister of Health with the Bugster Virus, while the doctors at the CR fall out over the most important course of action: Save the Patient or defeat Graphite?
Unable to control the powers of the new "Drago Knight Hunter Z" Gashat only by himself, Emu realizes that he must work together with the other three Kamen Riders to fully control it in order to defeat Graphite. However, no one among them want to cooperate with him, until he comes with an idea.
Emu gives Kiriya another chance to earn his trust. Kiriya then takes the chance to finally reveal Kuroto's intentions and expose him as the Black Kamen Rider that is working with the Bugsters.
With Christmas around the corner, Emu runs against time to defeat the Salty Bugster again and save another patient, while Kiriya's investigation leads him closer to the truth, but his life is in danger when he faces Kuroto's new power.
With the Bugster infection spreading rapidly, the authorities can't hide the disease from the public anymore. After Kiriya's death, Kuroto starts targeting the other Kamen Riders, but Parad approaches Emu, offering him a blank Gashat which will allows him to attain a new level of power.
Using the power of his new Gashat, Ex-Aid easily overpowers Genm and the empowered Aranbura Bugster, unaware that he is being used as part of Parad's scheme.
Taiga tries to find out more about Emu's infection, and starts to discover the secret that might be why Kiriya was killed.
The Revol Bugster reappears and much to Emu's surprise, stands up to defend him against Taiga and Hiiro.
A lovable hamburger Bugster named Burgermon appears. Emu transforms into Ex-Aid, but attacking it causes the game disease patient to suffer from stress. What is this?
Kuroto makes a new level 50 Dual Gashat, comprising of Taddle Quest and Bang Bang Shooting's data. However, his domination was cut short by Parad's wrath, after realizing that Kuroto only sees Bugsters as baits.
After losing his gashats to Kuroto, Hiiro managed to obtain the new Dual-gashat that Kuroto made, and unleashes the abilities of Brave at Level 50. With such power, surely there is a catch?
Seeing as Hiiro is unable to control the Dual-gashat for long, Taiga decides to claim ownership. Meanwhile, will Emu ever regain his confidence as a rider again?
Kuroto reveals the true meaning behind his 'level X' Dangerous Zombie, while Parad decides to join in the fun by challenging Taiga's Bang Bang Simulation.
Kuroto falls victim to the Bugster virus and is apprehended by the authorities. Despite everything Kuroto did to him and his friends, Emu is determined to treat him, but the others are wary, wondering if saving Kuroto's life is worth the effort, or a great mistake.
Recovered from his infection, Kuroto resumes his plans to complete "Kamen Rider Chronicle" and the members of CR seem to have no way to stop him, until Taiga gives Emu a new Gashat that brings forth a power never seen before.
After Kuroto's death, Parad moves on with his ambition to complete "Kamen Rider Chronicle", and when multiple individuals become infected with the Bugster virus, a warrior from outer space appears to lend Ex-Aid and the others a hand.
Still worried about Poppy's disappearance, Emu and Hiiro are dispatched to attend multiple occurrences around the city and not only discover what happened to her, but also that Parad completed "Kamen Rider Chronicle" and is using it to drag the population into the conflict.
Amidst the chaos brought by "Kamen Rider Chronicle", the CR has its activities suspended by the government, when Poppy herself joins the battle using a new Driver and Gashat to transform into a Kamen Rider.
Taiga confronts the new Genm Corp CEO Ren Amagasaki and discovers his true identity; meanwhile, Nico decides to join the fight using the power of "Kamen Rider Chronicle"; but will she use this new power for good, or will she finally take her revenge on M?
Hiiro, Taiga and Nico decides to confront Poppy, and intends to defeat her while Emu gets his hands full with Parad. Is this the end of Poppy Pipopappo?
Possessed by Parad, Emu fights him for the control of his body, and the true connection between them is revealed.
After defeating Ex-Aid, Brave and Snipe, Parad begins to manipulate Emu's body in order to retain his infection, but Poppy is determined to save Emu, and comes with an idea.
Everybody in CR is upset with Kuroto's mysterious resurrection, but Emu knows that he needs his cooperation to stop Parad and Kamen Rider Chronicle, although he can't trust him at all.
Kuroto's father, Dan Masamune, has been released from jail and decides to retain his position as the president of Gemn Corporation. But on what grounds? And what power does he hold?
Knowing that he needs a team to ensure his success, Masamune attempts to recruit Hiiro to his side, using Saki's data as bait. Meanwhile, Emu and Kuroto devised a plan to outsmart Cronus's "pause" ability.
Knowing that there is only one reason for Hiiro to betray his friends and join Masamune's side, Emu confronts him again, but he is unprepared for the next surprise that awaits him.
While Hiiro continues to work under Masamune in order to save Saki, Emu's path to victory is now obstructed by the return of Kiriya. Would Maximum Mighty X's reprogramming techniques turn the tide for CR?
Masamune holds a event "Beat the Cronus" to increase the players in "Kamen Rider Chronicle".
Using Saki's consciousness as a leverage, Masamune orders Hiiro to destroy Emu using the new Taddle Legacy Gashat, that upgrades his power to Level 100.
With Hiiro's operating abilities the only hope of saving Taiga, Masamune warns Hiiro of the consequences should he choose to save him. With two lives on the line, who will he choose?
Masamune infects Nico with the Gemdeus virus, that can only be cured by defeating Kamen Rider Chronicle's final boss, only accessed by defeating Parado and Graphite, leading to the decisive battle between Emu and his other self.
Emu has lost the ability to transform, and it's up to the other Riders to defeat Cronus and reclaim the Master Gashat. However, even with the power of Hyper Muteki, they are overpowered by him.
Hiiro and Taiga challenge Graphite for a final battle, not only to settle their scores, but to obtain the last Gasha trophy needed to summon Gemdeus in order to complete Kamen Rider Chronicle.
At last Gemdeus appears, and with its advent, the Bugster virus is spreading among the population. The Riders then must join forces to defeat him and put an end to Kamen Rider Chronicle.
The new and improved Gemdeus-Cronus hunts down Nico, bringing Emu, Hiiro and Taiga into initiating their final battle with him. When all else seem to fail, one particular individual becomes a second Cronus to assist in the ending of Kamen Rider Chronicle.
Gamedeus Cronus evolves into his ultimate form and starts a pandemic. To stop him once and for all, Poppy and Parado come with a desperate plan.
Despite that Gamedeus was finally destroyed, Emu can not transform into Ex-Aid Muteki Gamer anymore now that Parado is gone. He then must join forces with the other Riders for the final battle against Masamune.