scientist Keitaro Jin and his son Keisuke become caught up in the campaign of terror by an evil organization known as "G.O.D.". They are attacked and the professor's technology gets stolen, but before Keitaro dies, he is able to perform surgery on his son. With the last of his robotics technology, he transforms his son into "Kamen Rider X". To avenge his father's death and ensure the safety of the entire world, Keisuke uses this technology as he battles the monstrous minions of G.O.D..
Characters
Keisuke Jin/Kamen Rider X: The son of Keitaro Jin, Keisuke suffered mortal injuries inflicted by G.O.D when they attacked the Jins. As a result, with his father's final breath, Keisuke was made into an advanced cyborg developed for marine exploration called a "Kaizorg". Driven to avenge his father's death and save the world, X battles G.O.D..
Tōbei Tachibana: The mentor of the previous Kamen Riders.
Ryoko Mizuki: Keisuke's fiancée, Keitaro's assistant, and a G.O.D. member. She is an Interpol investigator and executes undercover operation in the G.O.D. She became a cyborg by G.O.D.'s operation. Her true identity was exposed while protecting a child from Strong Arms Atlas and she was destroyed by the G.O.D. General.
Kiriko Mizuki: Ryoko's twin sister who is an Interpol investigator. She died protecting Keisuke from Strong Arms Atlas' arrow.
Chiko: A student of Johoku University and Tōbei's coffee shop worker.
Mako: Chiko's friend and Tōbei's coffee shop worker.
Keitaro Jin: Keisuke's father, Keitaro was a robotics genius whose technology attracted G.O.D.'s attention. As a result, Keitaro saved his son's life at the cost of his own.
G.O.D.
The G.O.D. Secret Organization, short for the Government of Darkness, is the evil organization that X battles against.
G.O.D. General Commander: A mystery man who commands the monsters using various objects with tape recorders which record his commands.
Apollo Geist: The Chief of Security of G.O.D., armed with the Geist Cutter shield and the Apollo Shot shogun, his human appearance wears a white tuxedo with black gloves until he invokes "Apollo Change". He destroyed himself using his Arm Bomb after he was defeated by X's Finishing Kick.
* Apollo Geist Reborn: Revived by two doctors of G.O.D. Armed with the Apollo Magnum bayonet on his right hand, the Geist Cutter shield, and the small Geist Cutter shield on his left shoulder. He was Destroyed by X's X Kick.
King Dark: The leader of G.O.D., he reveals himself after Apollo Geist's destruction, mocking X. He was destroyed by a self-destroying function that Dr. Noroi started.
Dr. Noroi: Dr. Noroi is revealed to be the leader of the Government of Darkness. He was destroyed in King Dark's destruction after being stabbed by X's Ridol Whip.
G.O.D. Warfare Agents: Warriors who serve as foot soldiers for the Government of Darkness. Not only do they carry spears, they also wield pistols and machine guns.
;Kamen Rider X: Reedited episode 3. A little girl named Sayoko witnesses the murder of an Interpol agent by the G.O.D. kaijin Hercules. Keisuke Jin saves her before Hercules disposes of her. Sayoko tells Keisuke that G.O.D. is targeting an important official named Kibara. Kamen Rider X has his hands full when G.O.D abducts Kibara and takes Sayoko and her mother hostage. ;Five Riders vs. King Dark: During a motocross practice, Keisuke Jin is ambushed by two of G.O.D.'s kaijin warriors. He transforms into Kamen Rider X, but little does he know that his battle is recorded and analyzed by King Dark to create a super kaijin. Meanwhile, other G.O.D. kaijin are attacking children all over Tokyo. But before the other Riders intervene, the kaijin mysteriously disappear. Upon learning about King Dark's latest plans, Kamen Rider X joins forces with the four Riders to stop G.O.D. and their revived kaijin.
S.I.C. Hero Saga
The S.I.C. Hero Saga story for Kamen Rider X was published in Monthly Hobby Japan magazine in its July to September 2009 issues. The story was titled Masked Rider X: Son of Zeus. ;Chapter titles
