The Space Ironmen Kyodain siblings from space who plan on attacking the Earth and the main antagonists of the movie Kamen Rider Fourze the Movie: Everyone, Space is Here!
The Space Ironmen Kyodain were created by Professor Blink. However, after exposure to Cosmic Energy made them aware and see themselves as superior beings, Groundain and Skydain attacked the professor. Near death, professor activates a fail-safe that locks the Kyodain in human form. In order to get their powers back and start their plan, Groundain posed as the general manager Harumi Saeba of OSTO Legacy and recruited the Kamen Rider Club to deal with Black Knight and Inga Blink and power down XVII. With the Space Core powered down, the Kyodain regained their forms and attacked the Club before going on with their plan to use XVII to destroy humanity.
Kamen Rider Fourze in Cosmic States managed to stop their plan by warping the orbital laser back at XVII, ceasing its functions. The Kyodain then attack the powered down Fourze and Meteor. When it seemed hopeless, Fourze gained the power of the Fusion Switch and Fusion States. The Kyodain assumed their vehicle forms as Fourze rode on his Machine Massigler, before Fourze made the finishing blow with Fusion States' Limit Break, destroying the Kyodain.
During the events of Super Taisen Z, Groundain and Skydain are rebuilt as members of Space Shocker. However, finding themselves in debt to Gai Ikari and Gavan Type-G, the two act on their own sense of honor which eventually lead to their deaths.
- Groundain is the blue car-like older brother of the Kyodain. To begin his act of treason against humanity, he rushes to complete the military satellite weapon: the XVII. He is armed with a powerful cannon built into his chest called the Grounbuster X. Groundain is an homage to Grounzel from Space Ironmen Kyodain.
- Skydain is the red jet-like younger sister of the Kyodain. Like her brother, she gains her own personality and wants to rebel against humanity. She is armed with built-in blades in her arms. Skydain is an homage to Skyzel from Space Ironmen Kyodain.