Her father, Ryubee Sonozaki strictly raised Saeko to believe that their family is superior to all others and that they are destined to rule the world. This loveless upbringing caused her to grow up secretly hating her father, often taking the resulting rage out on her younger sister Wakana Sonozaki, serving as fuel for her own ulterior motives of taking over the Museum to prove herself to her father to be its ideal successor. She also has a tendency to kill her boyfriends if they do not live up to her expectations. Although Saeko initially spares Kirihiko Sudo due to his capabilities, even marrying him and letting him be a part of the Sonozaki Family, she kills him when he threatens the Museum's livelihood. She has no problems executing Kirihiko as she had never loved him. Later, she pay regular visits to Dr. Shinkuro Isaka to improve her Dopant form and focus on her plans for the Museum. After he is almost defeated by the Kamen Riders, she begins to show that she cares for Isaka's well-being, which is likely to be genuine attaction to the doctor.
While Sokichi Narumi and Shotaro Hidari infiltrated a top secret installation, seeking the "Chosen Child," whose powers were being used for evil, the alarm sounds and Saeko in her Taboo Dopant form along several Masquerade Dopants to fight Sokichi who transforms into Kamen Rider Skull. Sokichi's fedora is damaged by her during the fight. She later appears again as the Taboo Dopant shortly after Philip is rescued from the central chamber of the Gaia Tower and Sokichi had been shot to death. When Shotaro and Philip transforms into Kamen Rider Double for the first time, she flees just before the building explodes. (ep. 1, Movie War 2010)
One year later, Saeko is seen at Digal Corporation and working with her husband Kirihiko Sudo, distributing the Gaia Memories and becoming the Taboo Dopant to combat Kamen Rider Double. Later when she kills Kirihiko(ep.18) and begins regularly visiting Isaka to improve herself (ep.23), she forms a partnership with him to overthrow her father and tries to kill Wakana Sonozaki for not taking her side but the Smilodon Dopant drives her away. However, Isaka is defeated by Kamen Rider Accel Trial causing her coup to fail and she ends up on the lam. Saeko is hunted down by the Smilodon Dopant, who takes the Taboo Memory and leaves her for dead. She is then saved by Jun Kazu who offers his support in her scheme to take control of the Museum. After infiltrating the Digal Corporation, now with Wakana as its head, she obtains the Nasca Memory and then uses an L.C.O.G on herself instead of using the Memory with a Driver. Without inhibitions posed by a Driver, Saeko is able to use the Gaia Memory in its Level 3 state to become the R Nasca Dopant to overpower her sister. However, when Wakana evolves to ClayDoll Xtreme, which Saeko proves to be utterly powerless against, she is forced to go after other options to make herself more powerful, such as the Jewel Memory, before the Nasca Memory is destroyed in a confrontation with ClayDoll Xtreme. Later, after her father's death, Saeko is disillusioned until she learns of Wakana's survival and regains the Taboo Memory from Kazu after he announces that she has become the head of the Museum. However, no longer having a reason to prove herself with her father dead, Saeko fights Kazu in order to save her sister. As a result, the Taboo Dopant sacrifices herself to hold off the Utopia Dopant to give Wakana time to run away, resulting in Saeko's death as she finally admits the irony of her last moments in her final breath.
Video Game appearances
Kamen Rider Travelers Record
The Taboo Dopant appears in the video game Kamen Rider Travelers Record.
As a member of the Sonozaki Family, Saeko owned a Gaia Driver and a golden Gaia Memory, the Taboo Memory to become the Taboo Dopant. But when they are taken from her by the Smilodon Dopant, she uses her ex-husband's Gaia Memory in place of them until it is destroyed. She then regained her original Taboo Memory from Kazu which she used against him, which led to her death.
- Height: 200cm
- Weight: 72kg
The Taboo Dopant is Saeko's first Dopant form accessed through the Gaia Driver and Taboo Memory. In this form she has the appearance of a rag doll and gains the ability to fly and generate deadly bombs of intensely hot light. It was further increased in power due to some modifications to her Gaia Driver by Isaka, to the extent of being unaffected by certain Dopant powers such as that of the Yesterday Dopant. This form is lost after Mick as the Smilodon Dopant takes her equipment away and nearly kills her. She regained the Taboo Memory after Kazu presented it to her, the memory was destroyed by the Utopia Dopant in a fight against him.
R Nasca Dopant
- Height: 198cm
- Weight: 92kg
The R Nasca Dopant is Saeko's second Dopant form, unlike her previous Dopant form she used the L.C.O.G on herself to create a Living Connector to use the memory instead of a Gaia Driver which limits the powers of the memory. Unlike Kirihiko's form which is blue with red markings, Saeko's is an orangish-red and possesses greater speed and power due to being Level 3. The R in the name stands for both Red (the forms color) and Revenge (Saeko's feeling towards her father and sister). But when Wakana evolves into ClayDoll Xtreme Saeko went after other plans to empower herself further such as the Jewel Dopant. However the Nasca Memory was destroyed in a fight against ClayDoll Xtreme.