Jun Shibaura (芝浦 淳 Shibaura Jun) is Kamen Rider Gai (仮面ライダーガイ Kamen Raidā Gai, Masked Rider Gai), a fictional character in Kamen Rider Ryuki. He is the sixth of the 13 Kamen Riders the story revolves around.
He is a 3rd year college student at Meirin University, extremely well-versed in computers and programming to be in the Matrix Netgame Club. Being the son of a company president, Jun is arrogant in personality, toying with other people's lives for nothing more than a good laugh. He joined the Rider War simply to be the winner, which to him was all a game. Jun even used his Matrix members' thrill-seeking urge against them to fight to the death in a game similar to the Rider War while he watched from the shadows.
Investigating the matter, Shinji meets Jun when he reveals to the journalist as the mastermind behind the game of death. When the Mirror Monsters arrived, they transformed and fight one of the Mirror Monsters. After the defeating the monsters however, he later attacks Ryuki and steal his Dragreder card. He used both Shinji's card and the virus he uploaded to the ORE Journal mainframe to blackmail himself into their head of their company. Shimada eventually managed to wipe out his programming with her own virus, while Miyuki Tezuka stole back the Dragreder card. Soon after, Jun was picked up by the police for his ties to the Matrix member murders, getting his father to bail him out with Shuichi Kitaoka's aid.
Jun even went so far as to reveal the true identity of the other Riders among them, impressed with Takeshi Asakura's sadistic nature. To suit that end, Jun kidnapped Yui to start a "Rider party" between him, Kamen Rider Knight, Kamen Rider Raia, and Kamen Rider Ryuki. However, in the middle of the fight, their battle gets intertwined with the one between Kamen Rider Zolda and Kamen Rider Ouja, who used Gai as a shield to take the blunt of Zolda's Final Vent before killing him with his own hands. Metalgelas was infuriated at its master's death at the hands of Kamen Rider Ouja and went after him only to fall victim to Ouja's contract card.
Some time after his death, and the subsequent end of the Rider War due to a time distortion made by Kanzaki Shiro, Jun is revived. After his revival, he re-discovers his rider deck, and proceeds to re-instate his contract with Metalgelas.
Jun is very manipulative and intelligent, but also quite prideful, due to his father's wealth. It is this pride, and deceitfulness that would eventually lead to his death. He is shown to have little to no remorse for his actions, and is more than willing to injure innocent people to make things more interesting or fun for him. After being resurrected, this has not changed, with his view of the world still seeing it as a game.
- Height: 195cm
- Weight: 100kg
- Ability Perimeters
- Punching Power: 15t
- Kicking Power: 15t (300AP)
- Maximum Running Speed: 100m/5s
- Maximum Jump Height: 20m
Similar to Kamen Rider Scissors and Kamen Rider Tiger, Gai is a melee fighter who relies on brute strength and his intellect more often than anything else, Gai's attack methods usually involve his Confine Vent card to cancel any weapons from the other Riders while using the Metal Visor (メタルバイザー Metaru Baizā) on his left-shoulder to conjure his Metal Horn gauntlet as well as summoning his contract monster Metalgelas to fight alongside him and execute his Heavy Pressure (ヘビープレッシャー Hebī Puresshā) Final Vent, carried by his Contact Monster as a lance, with the Metal Horn extended in front of him to pierce through the opponent. Gai is a close range specialist. He uses brute force over his opponents, as well as his intellect. His strategies often involve overpowering his opponent with a combination of his powerful Strike Vent and his Contract Monster Metalgelas, as well as negating his opponent's Advent Cards through his strategically important Confine Vent.
- Jun's first name would eventually be given to Jun Maehara, who was also a silver colored Kamen Rider, being Kamen Rider Amazon Sigma.