Ultraman X (ウルトラマンエックス, Urutoraman Ekkusu) is the main hero of his series. Originally, he was an Ultra Warrior that chased his opponent, Greeza, to the solar system and banished it towards the sun, but doing so had triggered the Ultra Flare and cost him his physical body, permanently trapping him in the digitized state that he used for interstellar traveling. In the present day, he bonded with a Xio member Daichi Oozora and inhabited the young man's X Devizer in order to lend his strength in fighting against monster threats with his physical form.

The actual history behind X is unknown, except the fact that he is an Ultra Warrior whose mission is to maintain the balance of outer space. After Greeza had destroyed 3 planets, X chased the monster in their travel forms until they reached the solar system. His attempt to hurl Greeza towards the sun turned out to be fatal as it launched the Ultra Flare, awakening Spark Dolls on Earth.

Fifteen years later, when the monster Demaaga rampaged on a city, he rescued and bonded with a Xio officer Daichi Oozora. Their synchronization allowed the temporary restoration of his body and doing so to defeat Demaaga. A Voice From the Starry Sky After the battle, X seeks Daichi's help in recovering his physical body as the latter agrees to do so. Starting from his fight with Birdon, X gains the Cyber Armor ability from Alien Fanton Gourman, allowing him to use the power of Cyber Kaiju. A Collection of Possibilities Aside from fighting against Earth Kaiju, X also faced against alien invasions and received mutual support from Xio members. All for One

ZERO-X IV

On one mission, he met an Ultraman from another dimension, Ultraman Zero whom was hunting down Alien Nackle Bandello. X assist the Ultra after a Lab Team member, Rui, was accidentally brought along by Bandello, whom wanted their Spark Dolls. After the ordeal ended, Ultraman Zero bids farewell to Ultraman X, who hopes that they will meet again some other time. When the Aegis Shines Not long after Zero returned to his home, Gargorgon arrived on Earth in search of the Alien Gold named tE-rU. X and Xio members join forces with the alien refugee in against the destroyer before he threw himself to protect tE-rU. After being freed by his allies, X then used the newly created Bemstar MonsArmor to destroy Gargoron.

X had another encounter with an Ultraman from a different space. When Tokyo was being plagued by a Zetton, X and Daichi attempted to use the Zetton MonsArmor to combat it. But before X could do anything after acquiring the new MonsArmor, he was attacked by a virus placed on the armor by the Zetton's master Alien Sran Quila. Quila had infected X's armor as part of a grand scheme to lure out Ultraman Max and enact revenge on him. Upon Max's arrival on the battlefield, Quila controlled X through the MonsArmor, forcing him to assist Zetton in beating down Ultraman Max until Daichi cleansed the virus with Eleking. With their combined powers X and Max destroyed Quila and his Zetton.

After the battle Max encouraged X to always have faith in others as doing so is the source of strength of the Ultramen. X in Peril Max's power would be put to use by Ultraman X, who used it against the Pedanian robot, King Joe.

During the Gua Army's invasion, a strange dark energy frequently appeared, which was given the name Dark Thunder Energy. The army launched another Demaaga, which was empowered by a Dark Energy and had X on the ropes. Eventually, he was forced to separate with Daichi at the cost of his consciousness lost in cyberspace. After Daichi manages to rescue him with his newfound Xlugger, the Ultraman returned to the real world and gained a new form, Exceed X. Despite its capability to overwhelm Demaaga and purify it, it was unable to catch up with one of the army's leader, Mold Spectre until Daichi received swordsmanship training from Sho/Ultraman Victory. During their battle with the Gua Army, Ginga joined the fray, having destroyed a majority of their armada and finally with Xio's help, defeated the army and their leader. End of the RainbowSword of Victory The Shining Sky, and the Land Beneath It

X's battles continued due to the mysterious Dark Thunder Energy and in the middle of the conflict, he reunited with an alien from his past, Mu Wataru's Romance and finally teamed up with Nexus to destroy an invading Space Beast. Bond -Unite-

Following the arrival of his old enemy Greeza (whom he thought to have killed in the Ultra Flare), X was forced to reveal himself and openly seek cooperation with Xio to defend their supply of Spark Dolls from Greeza. Eventually, the resistance faltered and with Exceed X left, he dashed in and performed a kamikaze attack by self-destructing with Greeza, leaving his Color Timer intact. However, X's sacrifice was all in vain as Greeza reformed itself and successfully stole all of the Spark Dolls, achieving its final form. After Asuna rescued Daichi from cyberspace, his memory of X revived the Ultra as well and the two arose to fight Greeza again. Seeing Gomora's power being exploited by the villain, Daichi pleaded for Gomora's help and eventually all the Spark Dolls merge with X to form the Hybrid Armor, allowing them to finish the destroyer. With X no longer a secret to the Xio members, he was nonetheless accepted into the team, though he was yet to regain his physical form despite Greeza's destruction. He absolutely love his host daichi ozora

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