Jun Kadowaki

Kamen Rider Gaia is the main protagonist of Kamen Rider Eve -Masked Rider Gaia- and was supposed to be the original Shocker Hopper cyborg until he was put into further stasis and was not awakened until the 21st century. When he first appeared, he was more of a grasshopper kaijin, but later became more similar to the Double Riders while still appearing more organic.

Biography
Jun Kadowaki is a young man who was used by Shocker to become the original Hopper series cyborg but their plans changed after Takeshi Hongo escaped. When the Double Riders destroyed the Shocker base before Kadowaki could be awakened he was buried under the rubble for 30 years. Awakening in the 21st century, Kadowaki has no memories of his past and begins his quest to regain his memories while trying to figure out who turned him into a cyborg. Along the way he encounters the remaining Shocker Kaijin while changing from a kaijin to Kamen Rider Gaia.

Jun regains his memories over the course of the story. He was originally a high school student who lived with his father Junichiro Kadowaki and was part of the kendo club. Over the course of the series, Jun would have continuous mental encounters with the Great Leader of Shocker. With help from his now altered human father and Takeshi Hongo, the stone that gave Jun his powers was removed. The Showa Era Kamen Riders up to ZX then put some of their powers into Jun to keep him alive and give him a new form. Jun as the newly reformed Kamen Rider Gaia would fight against the Great Leader and after a hard battle defeats him with a Rider Kick but is consumed in an explosion. His current wherabouts are unknown.

Kamen Rider Gaia
As one of the original Hopper Kaijin, Kamen Rider Gaia possesses abilities like that of Riders #1 and #2. In his original Kaijin form, he was more feral and deadly but after gaining a form like that of the original Riders he becomes less vicious and more heroic.

Unlike the other riders of his generation, Gaia was given powers over nature with abilities to control weather, plants, and fire. It is later revealed that 'Gaia' is a special type of modified human based on the guidelines of the Great Leader. The source of Kamen Rider Gaia's powers is a stone that is attached to Gaia's belt buckle, without it Jun's body cannot be maintained; it also gives him a telepathic link to the Great Leader. The stone was eventually removed to keep the Great Leader our of Jun's mind. Kamen Riders #1-ZX put some of their power into a condition known as the Kamen Rider Syndrome that changed Gaia into a form similar to #1.

Machine Crusader
Machine Crusader is Kamen Rider Gaia's Rider Machine. It is similar in appearance to #1 and #2's Cyclones but the front wheel is rotational and possesses blades that can cut through obstacles and be used to attack enemies. The vehicle is also capable of going over most terrains. The back end possesses a smoke screen for easy getaways.

Trivia

 * While Gaia only exsists within Kamen Rider Eve, he is tied with Mutsuki Kamijou as being one of the youngest Kamen Riders; abducted and altered by Shocker at the age of seventeen.
 * Machine Crusader has the Smart Brain logo on some of its parts.