The younger brother of Ultraman Leo , Astra came from the desert Nebula L77 of the Leo constellation. After the destruction of L77 by the Alien Magma, Leo, Astra, and Leo's pet monster Ron were the last survivors, but Leo thought he was the last of his kind. As Leo and Ron landed on Earth, Astra was captured and held prisoner by the Alien Magma until he was eventually rescued by Ultraman King. After King told him of Leo's survival, Astra headed for Earth and rescued his brother during a battle against Garon and Littre. Ever since Astra has saved Leo against several different aliens over the months that were too powerful for Leo to defeat himself. At one point Alien Babarue froze Astra in a special type of ice in space and took his identity as he stole the Ultra Key. After Ultraman King revealed Babarue for what he was Leo saved Astra from his icy imprisonment, defeated Babalou, gave back the Ultra Key, and the two brothers became the first Ultra Brothers that were born outside of Nebula M78. Astra continued to help Leo after helping him destroy the Saucer Monster, Hangler.
Throughout the events of Ultraman Mebius, Astra is the least active of the Ultra Brothers. However. he is present during the series finale, assisting his brother Leo in using the Ultra Double Flasher in destroying the coating that was surrounding the sun.
Ultra Galaxy Mega Monster Battle Legends the Movie
Astra appeared in this film, watching over Ultraman Zero’s training with Ultraman Leo. When Seven’s eye slugger was sent as an S.O.S., Ultraman King sent Zero to the battle, followed shortly by Leo and Astra. When they arrived, Zero had already defeated Belial and blasted him in to a river of molten magma but no sooner had they arrived, the spirits of 100 monsters started to flow towards Belial and formed Beryudora. Leo and Astra then did their Ultra Double Flasher attack while every one else attacked Beryudora together until Zero finished him off. Astra and Leo then returned to the Land of Light with the others.
Ultraman Zero The Movie: The Revenge of Belial
Astra reappeared in this movie as he gave energy along with the other Ultras of the Land of Light to create Zero's travel sphere. He appears near the end to protect the Land of Light from the Darklops army and is beaten until Zero beats Kaiser.
Dark Spark War
Prior to the Ultraman Ginga TV series, Astra participated in the Dark Spark War but this time he fought not only alongside with the Ultra Brothers but, with the other Ultras that came from other universes and their allies against Evil. While in midst of battle, Dark Lugiel turned every Ultra alongside their allies, monsters, and aliens into Spark Dolls. With the war over an unknown warrior appeared and faced Dark Lugiel but like others, he also turned into a Spark Doll. The location of Astra's doll is unknown, but could be with Leo's Spark Doll, which is also unknown.
Astra returned to his original form along with all the Ultras after Ginga defeated Dark Lugiel.
Ultra Fight Victory
After Ultraman King sensed the awakening of the Space Emperor, he calls on Ultraman Hikari, Ultraman Ace and the Leo brothers.
Leo and Astra were sent to Planet Gua on the orders of King, to stop the revival of Juda. However, Yapool sent his Choju Battalions, Verokron, Doragory and Vakishim to take care of them.
While Leo and Astra were busy dealing with the Choju, Yapool arrived and the brothers watched as the super dimensional being used the Victorium he stole from the core to amp up Juda's revival.
Right after that, Ace, along with Ginga and Victory appeared to help Leo and Astra take down Yapool and his Choju Battalion. Astra defeated Doragory with his Astra Kick while Leo defeated Vakishim with his Leo Kick, Ace defeated Verokron with his Ultra Guillotine, and Ginga Victory defeated Yapool with his Ultra Fusion Shoot.
However, after Yapool exploded, the negative energies inside of him went to Juda's distorian and fully revived him and summoned Super Grand King Spector. Afterwards, Astra, along with the other Ultras tried to destroy Grand King with little to no success until Victory decided to take care of Juda himself while the rest deal with the robot before it destroys the planet.
Later, as Victory turned the power of the Victorium Core against Juda, the energies from the Core went into Super Grand King Spector, weakening him and Astra helped defeat the robot by combining his and Leo's Ultra Double Shoot with Ace's Metallium Ray and Ginga's Ginga Cross Shoot.