Yoshiko, operating under the alias Victoria, is a 19-year-old woman who crosses paths with Shinnosuke Nohara and his friends amidst their struggle against the environmental group Save Keeping Beautiful Earth (SKBE). Initially posing as an ally, she claims to oppose SKBE's "Human Animalization Plan," which seeks to transform humans into animals using a specialized liquid. She aids Shinnosuke and the Kasukabe Defence Force following their escape from SKBE operatives, offering them temporary shelter. Her commitment intensifies as she penetrates SKBE's underground headquarters beneath Kasukabe. During her mission to sabotage their operations, she is captured. Despite this, she succeeds in awakening and destroying vital components of the SKBE base, significantly disrupting their schemes. The climax reveals Victoria's true identity as Yoshiko Shizen, wife of SKBE leader Mamoru Shizen. Confronting Mamoru, she challenges his motivations for the animalization plan, born partly from despair over environmental destruction and her apparent disregard for nature. In a pivotal act, Yoshiko attempts to drink the animalization liquid herself to show solidarity. This compels Mamoru, driven by enduring love, to destroy the bottle and abandon his plan. His surrender halts the scheme, restores all transformed humans, and leads to the couple's reconciliation. Yoshiko's background as Mamoru's wife and her initial use of the alias "Victoria" define her role in the conflict. Her actions directly enable the resolution of the SKBE crisis and the restoration of the Nohara family.