A long time ago, the Earth was at the brink of destruction after King Demon Beasts wreaked havoc, but the monsters were sealed with the help of Ultra Warriors.

In the present day, these monsters were unsealed by Jugglus Juggler as cases of monster attacks started to appear in Japan. During Maga-Basser's attack, Gai made his debut by saving Naomi, the leader of the paranormal website SSP and started his mission to stop the resurrection of King Demon Beasts while taking refuge in the SSP's office. Unknown to the others, Gai secretly transforms into Ultraman Orb, a warrior of light who borrows the power of past Ultra Warriors upon losing his original form to fight against frequent monster attacks while facing Juggler, his original ally turned adversary after being rejected to be chosen for Orb's power. In the middle of the series, Juggler awakened the legendary monster Maga-Orochi who surpasses Orb in every of his available forms. Through the use of Zoffy and Ultraman Belial's powers as Thunder Breastar, Gai/Orb managed to defeat the infamous destroyer but his little control of its immense power almost killed Naomi when she was captured by Galactron. After learning to have faith in his strength, Gai manages to control Thunder Breastar and regains his lost form, Orb Origin.

At the end of the series, it was revealed that Maga-Orochi survived and matured into its original form Magata no Orochi. Its awakening was sensed by various monsters and aliens on Earth, with several of them already left Japan and caused an unstable change of climate. Juggler tricked the VTL Squad into launching their strongest missile, which unintentionally helped the monster in its revival while proceeding to consume the entire planet. Following Orb's defeat, he took this opportunity to taunt Gai by attempting to kill Naomi in front of him but failed to do so when she claimed responsibility of her own death. Juggler's action of saving Naomi brings forth a revelation that he had rescued her ancestor Natasha during the year 1908, allowing him to be redeemed in front of his own rival Gai. When assisting Orb in facing Magata no Orochi, Juggler held off the monster long enough for the Ultra to use his predecessor's powers and destroy it. In aftermath of the battle, Gai decided to depart on his travel once more while Juggler survived his apparent destruction and watched the former's departure from a safe distance.