"Revival Zero" is the one hundred and twenty-seventh episode of the Yu-Gi-Oh! ARC-V anime. It aired in Japan on October 16th, 2016 and in Canada on January 26, 2018. It became available with official subtitles via Crunchyroll on November 28, 2017.
In the midst of explaining, the Professor is interrupted by a notification of Yuya's intrusion into the inner chambers, slightly exhausted from his Awakening. Riley, Declan, and Yusho are relieved to see him, and Yuya hugs his father. The Professor then tells The Doctor to immediately begin the Revival Zero project as the Doctor stands no fighting chance against Yuya, but the Doctor expresses his overconfidence in his Parasite work and that as fellow researchers, they should be sharing a similar curiosity in confronting Yuya. The Professor agrees then turns the Doctor into a card, freeing the girls from his brainwashing in the process, as he expresses that his own past curiosity was what caused the Supreme King Dragon's birth in the first place.
The Professor reveals the girls and continues to tell his story of how he investigated a way to stop Zarc's fused form. By traveling the world and following the theory of Duel Monsters with souls while researching different natural environments, Leo was able to create four Spell Cards subtitled under the names "Flowers, Birds, Winds, and Moon" from the natural energy that he believed could counter Zarc. However, when Leo had just finished creating the four cards, Ray stole the cards, as she could not bear the thought of losing her father.
Leo tried to give chase to his daughter, but she activated one of the cards, destroying the surrounding buildings and blocking his way with rubble. Leo then took a different road and eventually saw Ray confronting Zarc, as she activated the four cards, causing the related natural energy sources of flowers, birds, wind, and the moon to react and converge within Ray's body. The reaction of natural energies then created the Four Dimension Bracelets on Ray's right hand. The natural energy convergence then caused a reaction in both Ray and Zarc's bodies, and subsequently de-fused the Supreme King Dragon from his dragons as well as Ray's and Zarc's original bodies into four, creating their dimensional counterparts and the Four Dimension Dragons.
When Leo opened his eyes next, he found himself flung back in time in the newly formed Standard Dimension where no ARC System or Fusion, Synchro, or Xyz Summoning existed. Suffering from partial amnesia and unable to remember who he was, Leo still retained his research skills, so he made his living by conducting experiments on the standard KaibaCorp Duel Disk, upgrading the incorporeal Solid Vision into the ARC System as it once was in the Original Dimension. Around this time, he met Yusho and created the Leo Institute of Dueling, together introducing Action Duels to the Standard Dimension. Later, Leo started to remember about his memories of the future, but was unable to guess why, so he created a machine that searched and visualized his future memories, making him realize that Ray was still alive, split within the Four Dimensions.(In the English Dub, the revelation of the girls' origin is stated at this point.)
Declan interrupts and elaborates with his view at that time, that Leo was so immersed in his incomprehensible research causing his mother to become erratic, and Declan, hoping to bring relief to his mother, wandered into Leo's lab and was transferred to Duel Academy in the Fusion Dimension.
Leo continues that when on Duel Academy searching for Ray, he instead found Celina, who resembled Ray in her childhood, but found no traces of Ray's memories in her. In his investigation, he concluded that Ray and Zarc must have been split into four and were reborn in separate four dimensions as Zuzu Boyle, Celina, Lulu Obsidian, Rin, Yuya, Yuto, Yugo, and Yuri respectively. Leo reveals the secret chamber behind him containing the carded people from different dimensions from the Arc Area Project and his intention to use their natural energy as a catalyst in the ARC-V Reactor that will refuse the separated Dimensions back into the Original Dimension as well as reviving Ray by fusing her dimensional counterparts as well (In the English Dub, Leo also states that the girls's existences will be erased in the process.), thus fulfilling Revival Zero's goal.
Having finished explaining his motives to Declan, Yusho, Riley, Yuya and Ray's Dimensional counterparts, Leo tells Declan to join him and defeat Yuya immediately, as the fusing of the Four Dimensions will not just result in Ray's fused revival, but Zarc's revival as well, opening the possibility that the Supreme Dragon King may be reborn and the only way to stop the undefeated Zarc for good is through a Duel. However, Declan rejects his father, stating that he has seen Yuya's true nature in his Dueltaining, which has brought genuine happiness to the people of different dimensions, and that as the founder of the Lancers, it is his and Yuya's shared duty to stop Leo's ambitions. The three activate their Duel Disks, and the Action Field Crossover is activated.
The following cards appeared in this episode. Cards in italics debuted here.