Emu, a clumsy pediatrics intern takes young Sota, who is suffering a mysterious illness, to the announcement event of the latest "Mighty Action X", Sota's favorite game. Emu became a medical doctor in order to save someone's life because his life had been saved once through surgery. However, a mysterious virus emerges from Sota's body and the event turns into chaos. Emu hears from Asuna, an employee of the Ministry of Health, that transforming into a Kamen Rider can save the patient. Emu takes on this "operation" and inserts the Mighty Action X Gashat into the Gamer Driver, transforming into Kamen Rider Ex-Aid!

Becoming Kamen Rider Ex-Aid, Emu now must serve as both a pediatrician and a member of CR. A gifted surgeon named Hiiro Kagami comes back from the United States and is not only the son of the director, he’s also Kamen Rider Brave. This results in a clash of ethics when it comes to dealing with patients.

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.

Emu meets Kiriya Kujo, a forensic pathologist who visits the Hospital. He wonders what this go-getter gamer seems to know about the Bugsters and Kamen Riders…

When the thief of the 4 new Rider Gashats 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…or is it?

The girlfriend of the student that the Bugsters were after has contracted the game illness. Hiiro transforms into Brave and succeeds in separating the Bugster from the girl as Graphite battles the Riders. After the battle, Taiga, who intended to “repay” Graphite for what happened 5 years ago, is cornered by Hiiro, telling him that he could have saved Saki. Who is this Saki? What happened between Taiga and Hiiro?

A hospitalized patient showing two symptoms of the game illness has appeared. Emu and Hiiro transform and succeed in separating the two Bugsters from the patient. But the Black Ex-Aid appears once again to interfere, letting the Bugsters escape. Kiriya appears before Emu to offer his help stopping the 5th Rider. An irritated Hiiro declines, since he feels Kiriya can’t be trusted. However, after the Bugsters appear again, Kiriya repeats his proposal to Emu.

Taiga manages to capture the Bugster which escaped during the last battle and obtains the Jet Combat Gashat, holding the Bugster, and thus the patient, hostage in exchange for the other Riders’ Gashats. When they arrive to challenge him, he decides only he is needed to fight the Bugster, and tries to destroy Ex-Aid and Brave.

Graphite infects Dr. Hinata Kyoutarou, the head of CR and the man who saved Emu’s life 16 years ago, 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 discovers that to do so he must convince the other Kamen Riders into join forces with him. Once he tricks them into doing so, the time comes for their showdown with Graphite.

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 terrifying 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 for their Gashats, but Parad approaches Emu, offering him a blank double Gashat which will allows him to attain a new level of power…

Wanting to save Dr. Shirakawa, Emu asks Hiiro to perform a surgery on his cancer. He has his Gashat back and faces the Bugster to also cure Shirakawa’s game illness. Will the surgery succeed? What will happen to Ex-Aid?! And what of his new split form?

Taiga tries to find out more about Emu’s infection and starts to discover the secret that Kiriya was killed over. Meanwhile, using data collected from fights with Mighty Brothers XX, Parad makes his move and reveals his new form: Kamen Rider Para-DX Level 50.

Emu thinks Taiga and Hiiro attacked him since he is the source of stress for Nico, who is suffering the Game Disease. He does not realize the true intention of the other two riders is to eliminate the Bugster virus residing in Emu himself, who is unknowingly infected with the disease as well…

A lovable hamburger Bugster named Burgmon appears. Emu transforms into Ex-Aid, but attacking it causes the game disease patient to suffer from stress. What is this?

In the last battle, Genm tells Emu that he saved the Bugster because his body told him to do so. Emu also suffers from serious headaches after every transformation since creating the Mighty Brothers XX Rider Gashat. And most of all, Emu lacks the compatibility surgery and yet he can still transform into a Kamen Rider. Everything is starting to come together, so what will Hiiro’s response be? Meanwhile, Dan Kuroto returns to Genm Corp., and using the Gashacon Bugvisor, he begins to spread the Bugster Virus…

Emu finally learns of the horrifying truth that he has the game illness. The Bugster virus in him acts up and he collapses to the ground, though for some reason no Bugster has appeared… Emu later wakes up in CR with his personality completely changed to that of “Genius Gamer M”. When a new Level 30 Bugster emerges, Emu transforms into Ex-Aid with delight and fights as if he were playing a game while no longer concerning himself with the patient. Just what has happened to Emu?

Taiga and Nico meet a high school student named Daisuke who is infected with the Bugster Virus and calls both Emu and Hiiro for their help. Parad suddenly appears and Hiiro faces him in his new form while Emu is hesitant on joining the fight.

Emu and Hiiro learned from Poppy that Kuroto was the one who had suggested Emu to CR. Meanwhile, a police detective is investigating the Zero Day case, causing him to interrogate Kuroto’s father, Masamune. During the investigation, he gets infected by the Game Illness. In order to save him, Emu confronts Masamune.

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 even if he will be grateful for it. On the other sides, Hiiro finds some very useful information from Kiriya’s belongings while Emu receives an emergency call that a Bugster is rampaging.

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.

The fierce battle between Ex-Aid and Genm has now come to an end. Meanwhile, a woman who was injured, Sora, is brought to Emu and Hiiro. Sora’s band members argue when suddenly all 3 of them are taken over by Bugsters! And on top of that, when Emu tries facing them alone, a young man appears, calling himself “Lucky!”

After Poppy’s sudden disappearance, Emu has been worried, but when a huge number of emergency calls come in, Emu and Hiiro are introduced to the next stage of the Bugsters’ plans, Kamen Rider Chronicle…

Kamen Rider Chronicle has begun! Para-DX has joined the game and defeated the first round of the general players, giving them a Game Over as Emu watched them disappear before him. Kamen Rider Chronicle is being sold at an extremely fast rate, and when a patient intends to cure himself, Emu gives chase, and is confronted by Poppy…

The CEO of the Genm corporation refutes the claim against his Kamen Rider Chronicle game by announcing that when a winner is announced, all of the people who received a "game over" will return to life. This marks a massive increase in players to the game... including Nico, who is yet again infected with the Bugster virus!

Emu is focused on bringing Poppy back to her original state. After restoring back Poppy's memory by using Maximum Mighty X's reprogramming ability, she tells Emu that she was born by possessing a human being.

Parado uses his Bugster power to posses Emu and challenges him to a fight as he finally unleashes his new Level-Up form.

Ex-Aid, Brave, and Snipe have all been defeated at the hands of Kamen Rider Para-DX Level 99! Much to the other Rider’s surprise, Poppy brings out a black Proto Mighty Action X Gashat and a Gamer Driver! Poppy found them thanks to her revived memories of a young Kuroto, as she seeks to use the power of Level 0, in the hopes of bringing Emu back to normal…

The CR team and Kuroto have a tough time working together, much to Poppy's displeasure; Taiga and Hiiro decide to combine their efforts to beat Kamen Rider Chronicle.

Kuroto's father is released from prison and Hiiro's father becomes a Ride Player; Kamen Rider Chronos enters the game.

After Dan Masamune harnesses Kamen Rider Chronicle to become Kamen Rider Cronus and eliminates Lovlica, the remaining Bugsters and CR’s Riders are stunned. Along with Cronus’ power to stop time, he seems to have stolen the Proto Gashats, depriving the Riders of the data of those who were deleted, forcing Emu to visit Masamune directly…

Hiiro’s betrayal weights heavily on the members of CR, but they know that if he’s working for Masamune, there can be only one reason. Parad and Graphite show up with a plan to use Gamedeus to defeat Cronus, while Emu is forced onto an emergency call where he comes face to face with Hiiro…

Apparently Hiiro wasn’t the only accomplice that Masamune had in the palm of his hand! Cronus suddenly summons Kamen Rider Lazer Turbo Level 0 into the fight! In order to further expand the presence of Kamen Rider Chronicle around the world, Lazer Turbo stands before the Doctor Riders in an attempt to keep them from ending the game! Much to the shock of everyone, Kamen Rider Lazer Turbo finally reveals his identity…

Genm Corp. announces a new addition to Kamen Rider Chronicle, a mission to defefat Cronus and harness his power, and despite knowing what dangers lie ahead, countless new players join the game! Meanwhile, Emu is still reminded of the message Kiriya said to him before Masamune took him away as Kuroto completes an invincible golden Gashat holding an unbelievable amount of hidden power!

Ex-Aid finally went Muteki and was able to beat Cronus! Masamune, who does not like the fact that Ex-Aid was able to attain a power that exceeded his control, angrily forces Hiiro to work for him as he claims Saki as a hostage! Brave forcibly renews his resolution, and this time he is able to transform into Legacy Gamer Level 100! Emu is more confused than ever, while Taiga is the only one who truly understands just how painful Hiiro's decision truly is…

Graphite mercilessly attacked the body of Taiga which forced him out of his transformation! The injured Taiga has been rushed to the hospital immediately, but there is a high possibility that his heart has been damaged. Moreover, it seems that it would take an expert-level of surgical expertise in order to save his life. After returning to Masamune, Hiiro's father and Asuna make an urgent phone call. The director asks Hiiro to perform Taiga's surgical operation. Just what decision will Hiiro come to in the end?

In order to deprive Ex-Aid of his transformation abilities, Cronus decides to target Parado directly. Para-DX without Emu is still not perfect, so he is beaten easily. Even so, Ex-Aid cannot stop chasing Cronus. However, Cronus was planning an underhanded scheme. Nico's game disease, which just started to show symptoms, belongs to that of Gamedeus, the Last Boss of Kamen Rider Chronicle! In order to defeat Gamedeus, Ex-Aid has to defeat both Graphite and Parado! Just then…Parado's hands begin to shake violently…

Parado has been defeated, and Emu has lost the ability to transform into Ex-Aid! Following Parado's annihilation, the other Riders team up in order to defeat Cronus. Brave, Snipe, Genm, and Lazer Turbo, all alternate the Hyper Muteki Gashat in order to counteract Cronus' Pause. Meanwhile, Emu was deep in thought. The fear of death that he felt at the moment of his extinction, even if he was a Bugster, he shared the same feeling as he did in that moment. Just then, Emu takes out the Mighty Brothers XX Gashat…

Kamen Rider Chronicle has been reset thanks to Masamune's special ability! Thanks to his Bugster infection, his hidden power has awakened, and the game is reset to the moment before Emu received the Hyper Muteki Gashat! Finally, with Parado having already been defeated, Graphite is the only game character left in order to clear Kamen Rider Chronicle! Brave and Snipe both challenge Graphite with a burning fighting spirit. Meanwhile, Emu believes that Graphite infected with Gamedeus' virus may be the only one strong enough to defeat Cronus. However, Graphite refuses to cooperate with the Riders…

The Last Boss of Kamen Rider Chronicle, Gamedeus, is finally born! If you defeat Gamedeus, then the game will end! However, at the moment of Gamedeus' revival, massive amounts of the Bugster Virus spread throughout the city! The number of infected patients are increasing, as well as the number of people being rushed to the hospital. While the doctors attend to the patients, Ex-Aid and Para-DX team up to fight Gamedeus! But their strength is far too weak against Gamedeus, as he sends them flying easily. At the same time, two people were confronting each other. Kiriya and Kuroto, both transformed, clash fists to see who's fate will be decided in the end…

Suddenly, the Gamedeus virus begins spreading through the streets! Masamune becomes Gamedeus Cronus and appears before the other Riders, as he summons Nico into the World of Kamen Rider Chronicle! Nico is the one who is qualified to challenge the Last Boss of Kamen Rider Chronicle as a Ride-Player, but it seems clear that Masamune is going to try to Game Over the player who is closest to beating the game in order to reset it. In an attempt to save her but unwilling to let the others follow, Taiga uses the Chronicle Gashats seized from patients and goes to find her. However, the other Riders cannot enter the World of Kamen Rider Chronicle! Just what will happen to Nico's fate?

Gamedeus Cronus has grown massive and become the strongest Last Boss! The Gamedeus Virus expanded and the pandemic has gotten worse. The Gamedeus Virus can now be transferred from person to person, turning the infected into Bugster Virus foot soldiers! Two Bugsters witnessing this symptom, Parado and Poppy Pipopapo, decide to take action. "There is something that only us Bugsters can do…" Poppy says as she rushes to Ex-Aid…

Though Gamedeus was finally destroyed at the cost of Poppy Pipopapo and Parado when they extracted the Bugster from his body, Masamune Dan survived and takes advantage of Emu no longer being able to use Hyper Muteki. The Kamen Riders are at a huge disadvantage, while Cronus doesn't hold back, and initiates Pause. All of the Kamen Riders' movements are frozen in time, and he prepares to kill them, starting with Emu…