Kamen Rider Wiki
Icon-exaid.png This article is about a monster in Kamen Rider Ex-Aid.

A Bugster Union (バグスターユニオン, Bagusutā Yunion) is the monster form of a Bugster-infected patient when the virus first flares up.


Bugster Unions are formed when a Bugster-infected patient experiences enough stress, the Bugster viruses inside multiplying rapidly and overtaking the patient's body, forming a giant orange virus form around it; the Union's shape seems largely irrelevant to the Bugster's appearance. 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.

The Bugster Union stage is bypassed for Bugsters in Level 3 or more.


Salty Bugster Union

A golem-like Bugster Union emerges from Sota Suyama's infection, rampaging at the release event for the game Mighty Action X. It is defeated by Ex-Aid Action Gamer Level 1 using a Speeding-Up Energy Item and the Gashacon Breaker, releasing the Salty Bugster. I'm a Kamen Rider!

Aranbura Bugster Union

A bacteriophage/wall torch Union emerges from Rensuke Natori's infection at a public fountain, being fought by Brave and Ex-Aid Quest and Action Gamers Level 1. It is cut in half by Brave's initial sword, releasing the Aranbura Bugster. Another Prodigy with No Thank You?

Revol Bugster Union

A floating pistol Union emerges from Yuki Kitami's infection in a park, quickly being destroyed by Snipe Shooting Gamer Level 1's body-bullet attack, releasing the Revol Bugster. BANG, That Jerk is Coming!

Motors Bugster Union

A spiked wheel Union emerges from Yoshitaka Nishiwaki's infection, fighting Snipe and Lazer Shooting and Bike Gamers Level 1. It is destroyed by Lazer, releasing the Motors Bugster. An Operation Called Dash!

DoReMiFa Collabos Bugster Union

A floating aquatic creature Union emerges from Yoko Horiuchi's second infection, fighting and being defeated by Brave Level 1 with a rapid flaming attack, releasing the DoReMiFa Collabos Bugster. A Hollow Beating in the Heart!

Giri Giri/Jet Collabos Bugster Union

A massive two-headed Ouroboros serpent Union emerges from Yoshio Okada's double infection in the CR patient ward, fighting Ex-Aid and Brave Level 1 after being Stage Selected to a rocky shoreline. It is destroyed by the Riders, releasing the Giri Giri and Jet Collabos Bugsters. The Reason for Some Lies!

Hunter Gamer Union

A dragon Union emerges from Kyotaro Hinata's infection from the Proto Drago Knight Hunter Z Gashat, separating from him to form instead of taking him over. It easily overpowers Ex-Aid and Brave Level 1, growing stronger before being challenged by Snipe Combat Shooting Gamer Level 3, eventually being destroyed by Ex-Aid Action Gamer Level 2 with a dual Mighty/Taddle Critical Finish, releasing the pieces for the Hunter Gamer to complete the Drago Knight Hunter Z Gashat. Beat Up the Dragon!

The dragon Union is briefly summoned again by Genm Zombie Gamer Level X while using a dual Taddle/Drago Knight Critical Finish against Brave Fantasy Gamer Level 50, but it is easily destroyed by Brave's counterattack. A Sudden Fantasy!?

Combined Union

Genm Level 10 merged a horde of zombie Bugster Viruses into a Bugster Union form combined from the first several, with the body of Salty's golem, Aranbura's wall torch for a tail, Revol's pistol for a right hand armament, and a pair of Motors' spikes wheels for shoulder pads. It is destroyed by Ex-Aid Maximum Gamer Level 99 before being immediately reformed by Genm, but is reverted to the crowd of zombie Viruses by Maximum Mighty Critical Finish. Extreme Dead or Alive!

Gamedeus Bugster Union

Para-DX and Graphite went to the world of Kamen Rider Chronicle to obtain a virus sample of Gamedeus as a quick countermeasure on Cronus. Here, they meet a sliver Bugster Union which appears in the shape of Gamedeus. The Bugster Union rampages and attacked the Bugster duo, until Graphite eventually obtained a sample with his Bugvisor and the duo left the game. Go Together, Embracing Your Ambitions!

Super Gamedeus

Upon entering the second phase of his boss fight, Gamedeus Cronus transformed into Super Gamedeus and wreaked havoc on the city. White Coat License The Riders’ most powerful forms seemed helpless to stop it, until Emu realized that Super Gamedeus was essentially a powerful Bugster Union. Ex-Aid, Brave, Snipe, Lazer, and Genm all assumed their Level 1 forms and attacked Super Gamedeus, eventually succeeding in excising Masamune Dan’s body from the giant Bugster Union and depriving him of his Gamedeus Cronus form, though he retained access to Gamedeus’s weapons. The remaining virus of the Super Gamedeus Bugster Union was subsequently neutralized by the sacrifice of Kamen Rider Para-DX using the Doctor Mighty XX Gashat. The Last Smile


Behind the Scenes

Like most giant monster forms, all Bugster Unions are completely CGI. Likely as a result and to minimize the budget, Bugster Union battles are often short or the audience is given only a limited view of the action to reduce the Unions' onscreen time.


  • It is unknown how Ex-Aid was able to defeat the Dragon Bugster Union in Level 2 when Asuna Karino stated that a Kamen Rider can only defeat a Bugster Union in Level 1, though because it separated from the infected patient instead of consuming them, it may have been a different type of Union.
    • Alternatively, only defeating a Union in Level 1 may have been because stronger forms would risk injuring the patient trapped inside, and since the Dragon Union had no patient inside, there was no risk.
  • The nature of how to deal with the Bugster Virus being dependent on its form is similar to how certain viruses require different procedures or methods of treatment even if similar in nature. If true, then the stability of Unions may be such that only the lowest levels are able to safely eliminate them without taking the patient with it.
    • This theory would explain how Bugsters of higher Levels pose less of a risk to the patient when using sufficient force to eliminate them, especially when possessing their bodies while active.




Icon-exaid.png Kamen Rider Ex-Aid
Kamen Riders
Emu Hojo - Hiiro Kagami (Game World) - Taiga Hanaya - Kiriya Kujo - Kuroto Dan - Parado - Asuna Karino/Poppy Pipopapo - Masamune Dan - Ride-Players (Nico Saiba - Haima Kagami) - Genm (Bakusou Treasure) - Kagenari Nagumo - Ninja-Player - Black Parado
Game Scope - Gamer Driver - Kimewaza Slot Holder - Rider Gashat - Energy Items - Buggle Driver (II) - Bugster Buckle - Gashat Gear Dual (β - Another) - Rider Gauges - Rider Gashat Case - Energy Item Holder
Gashacon Weapons
Gashacon Breaker - Gashacon Sword - Gashacon Magnum - Gashacon Sparrow - Gashacon Bugvisor (II - G) - Gashacon Key Slasher - Gashacon Parabragun
Other Weapons
Flamber Saber - Ride Weapon - Fuma Sōzantō - Genin Weapon
Robot Gamer - Beat Gamer - Combat Gamer - Chambara Gamer - Sports Gamer - Hunter Gamer - Bike Gamer - Burger Gamer - Fantasy Gamer - Simulation Gamer - Maximum Gamer - Safari Gamer - Tank Gamer - Legacy Gamer - Pac Gamer - Famista Gamer - Xevious Gamer - Galaxian Gamer
Asuna Karino - Haima Kagami - Kyotaro Hinata - Ginko Yumita - Nico Saiba - Satsuki Ogimachi - Mizuki Nishikikoji - Tsukuru Koboshi
Others: Saki Momose - Sakurako Dan - Eight Kirino - Saiko Yaotome
Locations: Seito University Hospital - CR - Ministry of Health - Hanaya Game Illness Clinic - Genm Corp. - Game World - Machina Vision - Next Genome Institute
Generals: Parado - Graphite - Ren Amagasaki - Gamedeus
Movie-exclusive: Michihiko Zaizen - Pac-Man Virus - Hatena Bugster - Soji Kuruse - Kazushige Ryuzaki - Ageha Takeda - Johnny Maxima - Nebula Bugster
Stageshow-exlusive: Futago Bugster
Regular Bugsters: Bugster Virus - Bugster Union - Salty Bugster - Aranbura Bugster - Revol Bugster - Motors Bugster - Collabos Bugsters (Gekitotsu - DoReMiFa - Giri Giri - Jet - Kamen Rider Genm series) - Burgermon Bugster - Gatton Bugster - Vernier Bugster - Kaiden Bugster - Charlie Bugster
Regular Games: Mighty Action X - Taddle Quest - Bang Bang Shooting - Bakusou Bike - Gekitotsu Robots - DoReMiFa Beat - Giri Giri Chambara - Jet Combat - Shakariki Sports - Drago Knight Hunter Z - Dangerous Zombie - Mighty Brothers XX - Perfect Puzzle - Knock Out Fighter - Perfect Knock Out - Ju Ju Burger - Night of Safari - Bang Bang Tank - Taddle Fantasy - Bang Bang Simulations - Taddle Legacy - Maximum Mighty X - Kamen Rider Chronicle - Toki Meki Crisis - Hyper Muteki - Doctor Mighty XX - Mighty Creator VRX - Hurricane Ninja - God Maximum Mighty X - Knock Out Fighter 2 - Zombie Chronicle - Mighty Novel X
Legend Rider Games: Let's Go Ichi Gou! - Adventure Guy Kuuga - Agito of the Sun - Mirror Labyrinth Ryuki - Moshi Moshi Faiz - King of Poker Blade - Taiko Master Hibiki - Insect Wars Kabuto - Time Express Den-O - DokiDoki Makai Castle Kiva - Barcode Warrior Decade - Detective Double - Jungle OOO - Space Galaxy Fourze - Magic The Wizard - Toukenden Gaim - Full Throttle Drive - Kaigan Ghost - Kamen Rider Build - Ganbarizing
Legend Games: Pac Adventure - Famista - Xevious - Taiko no Tatsujin - Galaxian
Other Games: Hatesate Puzzle - Buddhist Priest of Temple - Chou Super Hero Taisen - Chou Shocker Taisen - Bakusou Treasure - WayoseTUNE - Nazo Toki Labyrinth