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This article is about a/an monster race in Kamen Rider Ex-Aid.
Kamen Rider Ex-Aid
Bugster (Bacteria)
Generals and other Notable Members: Parad
Graphite (deceased)
Kuroto Dan
Monster Types: Bugsters
Grunts/Footsoldiers: Bugster Virus
Battled: Kamen Rider Ex-Aid
Kamen Rider Brave
Kamen Rider Snipe
Kamen Rider Lazer
Coexisted with: Genm Corp.
Next Genome Institute
Chronological/Production Order

The Bugsters (バグスター Bagusutā), otherwise described as game illness (ゲーム病 Gēmu-byō), are a type of computer virus and the main antagonists of Kamen Rider Ex-Aid.


The Bugster virus is a variety of computer virus. It was born from the glitches in the 10 games that Genm Corp. had in development five years ago, and most Bugsters seem to be based on characters from these games. Unlike most malware, the Bugster infects human beings, replicating until they take over their host's bodies, eventually causing the host to disappear and be completely taken over. The only way to treat the victim is to use the Gamer Driver to remove the Bugster from the host and then destroy it before the virus completely takes over.

Many patients appear to be singled out and infected directly, often by Graphite using the Gashacon Bugvisor. The growth of the virus withing the patient is triggered by stress, leading to a weakening of the patient's immune system. When it first flares up, the infection takes over its host's body, transforming it into a giant virus-like Bugster Union monster. Bugster Unions can only be defeated by a Kamen Rider in Level 1; the reason why is unexplained, though it may be because other Levels are too strong and may injure the patient inside the Union. Once the Union is defeated, the Bugster itself manifests from the virus debris, and can call Bugster Virus foot soldiers to help them fight. The patient begins fading away, eventually will fade completely and die, letting the Bugster become a complete being.

There are two ways to cure the patient from Game Disease:

  1. Defeat the Bugster who infected the patient.
  2. Perform a "GAME CLEAR" according to the rules of the game that the Bugster infected, so the Bugster may survive depending on the rules.

The only currently known complete Bugster is Graphite. If a patient dies from some other means first, it appears as if the Bugster connected to them will also eventually die.

Most Bugsters don't have their original personas. Instead, some of the characters from the video games that they have infected will manifest as Bugsters' persona while the Bugster act as their bodies.

As hinted by Parad, unlike humans/riders who will be "Game Over" if killed, Bugsters can always "Continue" to infect more victims. It was demonstrated by the reappearance of Salty Bugster.

Bugsters can also "Level Up" like game characters,in a similar manner of the mutation of general virus to against vaccines .


The first Bugster outbreak took place five years before the series. Not much is known about the incident at this time, designated "Zero Day". CR was founded by the joint efforts of the Ministry of Health and Seito University Hospital to fight the Bugsters.

In the present day, the Bugster virus re-emerged. The first known victim was a boy named Sota Suyama, who was infected by the Salty Bugster. Hoping to make the boy feel better (and not realizing the severity of the condition), his doctor Emu Hojo brought him to the release of Mighty Action X, where the Bugster took over Sota's body. In the resulting chaos, Emu was able to use the Gamer Driver and become Kamen Rider Ex-Aid, removing the Salty Bugster and defeating it, saving Sota. I'm a Kamen Rider!

The next known case was Rensuke Natori. The progression of the Bugster may have been provoked by the stress of his fiancée calling off the wedding. Another Prodigy with No Thank You?

BANG, That Jerk is Coming!

An Operation Called Dash!

Everyone Gathers for a Clashing Crash!

A Hollow Beating in the Heart!

Final Story (Special Edition): Future! Connected Thoughts!

The Reason for Some Lies!

Men, Fly High!

Beat Up the Dragon!

Uneven Doctors!

Who's the Black Kamen Rider?

Christmas Special: Targeting the Silver X mas!

Defined Destiny

We're Kamen Riders!

A New Challenger Appears!

The Paradox Who Defeated M

A Nonstandard BURGSTER?

The Truth Exposed

A Sudden Fantasy!?

Take Off Against the Direction of the Wind!

Chasing the Mystery!

Engineered History!

Extreme Dead or Alive!

Ambitious Go Together!

Other Events

"Tricks": Virtual Operations

Ex-Aid Chapter

Snipe Chapter

Genm Chapter

Dr. Pac-Man vs. Ex-Aid & Ghost with Legend Rider

Kamen Rider Heisei Generations: Dr. Pac-Man vs. Ex-Aid & Ghost with Legend Rider

"Tricks": Kamen Rider Genm

Part. I: Legend Rider Stage

Part. II: Legend Gamer Stage

Major Bugsters

Minor Bugsters


Other Bugsters



  • All Bugsters are designed by Katsuya Terada who is well known for designing the Dopants.
  • The Bugsters being genetic viruses given humanoid form is reminiscent of the Amazonz, especially when they begin to spread out as seen with the sequences shown.
  • The virus effectively replacing the host, assuming a large form before taking on a more humanoid frame, is reminiscent of the Phantoms of Kamen Rider Wizard
    • Unlike the Phantoms, however, the virus does not necessarily use the original body when the virus claims the infected host, such as the case of Graphite's host being different from the human form it currently possesses.
    • But the way they are cultivated with their cultivators working in pairs is similar to the way the Makamou are cultivated.
  • Given the series' gaming motif, the revived Bugsters altered appearance and additional abilities is likely a reference to enemies becoming more powerful and possessing new or enhanced abilities at higher difficulty levels.
  • Bugsters' weapons possess their owner's name: ex. Salty Bugster's Salty Knuckle.



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