|This article is about a/an villain and later, ally in Kamen Rider Ex-Aid.|
- "If our experiment succeeds, the very concept of life will change."
- ―Saiko Yaotome[src]
Saiko Yaotome (八乙女 紗衣子 Yaotome Saiko), born Saiko Zaizen (財前 紗衣子 Zaizen Saiko), is a doctor of the Seito University Hospital Centre for Regenerative Medicine in Kamen Rider Ex-Aid Trilogy: Another Ending. She is the daughter of Michihiko Zaizen.
Saiko's father, Michihiko Zaizen, was a doctor. Having watched him work, she followed his profession. Circa 2010, her father was lost to the Game Disease, having been employed by Genm Corp. CEO Kuroto Dan to surgically recover the Bugster Parado from Emu Hojo. Seeking to restore her father, Saiko pursued a career in regenerative medicine, and would head the initiative to restore those lost to the Game Disease following the demise of Masamune Dan in 2016.
Return of Masamune Dan
From the fact that Bugsters retained the memories of their human hosts, Saiko determined that they retained their residual genetic material. Having investigated every possibility, Saiko and her team came to the conclusion that the only option to restore those erased by the Game Disease was by reconstructing their human genes from the Bugster whose virus they had fallen to. Recovering the Kamen Rider Chronicle Gashat from Taiga Hanaya, Kuroto Dan was able to revive his late father Masamune Dan, and had Saiko extract the Bugster Black Parado from his body.
Saiko commissioned the creation of the Bugvisor G from Tsukuru Koboshi, current CEO of Genm Corp. This new games console served as a platform for the Let's Make a Bugster, a game which could theoretically transform Bugsters into humans, which would mark a great step towards restoring the victims of the Game Disease. Once the games console was completed, Saiko personally approached Parado and Asuna Karino to request the former's assistance in an experiment for Regenerative Medicine. After Asuna took her leave, Saiko used the opportunity to capture the remaining Bugster via the Gashacon Bugvisor. Saiko proceeded to deposit Parado at the Next Genome Institute, where he was binded in cables embedded with Level 0 data from Dan's Proto Mighty Action X Origin.
Soon after, Saiko and Tsukuru presented the Bugvisor G to Emu Hojo and Poppy Pipopapo. Enlisting Parado, actually the Black Parado, and Poppy as participants for the experiment, Saiko had them fitted with neckbraces sporting the gauges which indicated their progress in clearing the game. While leaving the Black Parado to play with Emu, Saiko conducted her experiment with Poppy personally. To start, Saiko suggested Poppy play a game of dress-up, which she obliged by using her own powers as a game character to change her attire in quick succession. Saiko, however, pointed out to Poppy that it would be more appropriate to wear clothes made for humans, as the aim of the game was to become human. To that end, Saiko took Poppy to a clothes store, the same clothes store that Masamune Dan had taken his wife Sakurako Dan just prior to the birth of their son. Inside, Poppy tried on a succession of costumes before ultimately donning the dress once worn by her late host, Sakurako Dan. Satisfied that Poppy was approaching the Game Clear, Saiko captured her in the Bugvisor.
Meanwhile, Emu had been sent to hospital as a result of injuries inflicted by the Black Parado. Making her way to the Next Genome Institute, Saiko inadvertently crossed paths with Kiriya, who noted that she had neglected to inform him of the new game. Saiko feigned concern for Emu and her ignorance of how the incident occured. Kiriya, however, grew suspicious of her and, recalling her father, rhetorically asked if she would dishonor him. Kiriya was infact well aware that Saiko Yaotome's father was infact the infamous Michihiko Zaizen.
Returning to the Next Genome Institute, Saiko left Parado to the mercy of his counterpart before joining Kuroto at his residence where Poppy was contained. As Kuroto left to confronted his father, Saiko presented to Poppy a batch of cherries, the favorite food of Sakurako Dan, which she attempted to forcefeed to Poppy so as to bring her closer to her host. As Saiko revealed to Poppy, her true goal in creating Let's Make a Bugster was to restore Game Disease victims through the sacrifice of Bugsters; as Poppy and Black Parado were respectively derived from Sakurako and Masamune Dan, their genetic codes would be combined to restore Kuroto Dan's human body. At this point, she was interrupted by Parado, who used the human genes inherited from Emu Hojo to set himself and then Poppy free. With Black Parado returning to fight his counterpart, Saiko summoned a reconstruction of Genomes, the ultimate life form created by her father, to engage Poppy, intending to eliminate both Bugsters. Eventually, however, Parado and Poppy prevailed against their opponents, with Genomes destroyed while Black Parado was on the brink of defeat at the hands of his counterpart.
Nevertheless, Black Parado had by this point reached the power of a genius gamer and was retrieved by Kuroto Dan's Gashacon Bugvisor II. However, much to Saiko's shock, Kuroto announced that he had no intention of becoming human again, revealing that his plan was to combine his skill as a genius game creator with the power of a genius gamer to achieve the talent of a god. As such, Kuroto informed Saiko that she was no longer of any use to him. Though abandoned by Kuroto, Saiko was approached by Parado and Poppy who, despite the abuses she inflicted upon them, pleaded with her to continue her work in restoring the victims of the Game Disease. Conflicted by the realization that the Bugsters had human hearts, Saiko took her leave without giving an answer.
Following her disassociation with Kuroto Dan, Saiko failed to appear at Seito University Hospital, making no contact with her fellow doctors. While considering her own future, Saiko was accosted by one of the Zombie Gamers brought forth by Dan's new game Zombie Chronicle. Though willing then to accept her death, Saiko was saved by Kiriya Kujo as Kamen Rider Lazer. Kiriya explained that he knew her story as well as what she betrayed, however, he insisted that she was the only one who could perfect the Regenerative Medicine and bring back those lost to the Game Disease.
Seeking to repay Kiriya for his act of compassion, Saiko summoned the navigator of Zombie Chronicle, appearing in the form of Kuroto Dan. Asking how the world would be revolutionized, Saiko was informed that it depended on the game's ending. Returning to Seito University Hospital, Saiko learned that Kiriya had left to confront Kuroto Dan alone. Reuniting with Emu, Parado, and Asuna, Saiko presented the Bugvisor G, noting that each game Kuroto created had a meaning, while insisting that Kiriya must not die. With the Bugvisor in hand, Asuna and Saiko set off to catch up with Kiriya. However, before they could intercept him, Saiko was caught by a Zombie Gamer, which infected and transformed her into a Bugster Virus zombie who proceeded to attack Poppy. Ultimately, however, Kuroto Dan was finally defeated by Kiriya, using the Bugvisor II left to him by the dying Masamune. As a result of Kuroto's demise, Zombie Chronicle ceased and so Saiko and all others infected by the zombies were restored to their original forms. However, Kiriya too sustained a Game Over, causing him to vanish alongside Kuroto.
Following her recovery, Saiko retrieved the Bugvisor G. By applying the mechanics of Let's Make a Bugster, Saiko had Kiriya's human genes analyzed and reconstructed before resetting them to their base state, leading to the restoration of Kiriya Kujo in his human form in an operation headed by Hiiro Kagami. A vital component of this operation, however, was ironically the reprogramming ability of the God Maximum Mighty X Gashat left behind by Kuroto Dan. Through further research of God Maximum Mighty X, Saiko predicted that it would greatly change the future of regenerative medicine.
Saiko's sole purpose was to revive her father to get revenge on the Doctor Riders. In reality, she is revealed to be nothing more than a tool for Kuroto's plan to create his ultimate game. Eventually, she is able to forgive the Doctor Riders and cooperates them to take down Kuroto Dan.
Behind the Scenes
Saiko Yaotome was portrayed by Yurina Yanagi (柳 ゆり菜 Yanagi Yurina)
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