Masako Yamada, who used the cosplayer alias Miyabi, is the deceased mother of Yumeria Moegi, also known as Akiba Yellow. She was a highly regarded and famous cosplayer, a passion that her daughter inherited and pursued in her own life. Five years before the events of the series, Masako died in a car accident, leaving a profound impact on her daughter. Yumeria constantly thinks of her mother, especially around her birthday, and this lingering grief becomes a central emotional point in the narrative. During the course of the story, a Delusion World version of Masako is conjured, allowing the Akibarangers to join forces with her to fight the monster Kabukichō Mesugurohyōmonchō. In this delusional form, Masako temporarily takes on the role of Akiba Yellow, fighting alongside her daughter and the team. Her character is defined primarily by her past as a celebrated cosplayer and her enduring influence on Yumeria, serving as a source of inspiration and a reminder of the bond between mother and daughter. Her notable abilities stem from her cosplay expertise, and in her delusional reappearance she is capable of wielding the powers of Akiba Yellow. Her role in the story is largely that of a motivating memory and a brief, tangible connection from the past that helps the Akibarangers in their fight.