Miyako Gotokuji lives as a middle school student with her grandmother in an ancestral Japanese home, speaking with polite honorifics. After exposure to white Chemical Z radiation during an ecological incident in Tokyo Bay, she transforms into the superhero Rolling Bubbles. Her superhero form employs a bubble wand to generate versatile bubbles for offense, defense, and rescue operations, featuring the signature "Bubble Poyon" technique for shock absorption and containment. A magical-girl-style transformation sequence activates via a specialized belt trinket, with powers contingent on maintaining her superhero outfit.

Personality-wise, Miyako blends general ditziness with situational maturity and harbors strong fashion interests. Male classmates admire her perceived elegance. She communicates with animals and typically displays gentle behavior but exhibits extreme anger when provoked. Her emotional resilience surfaces through unrequited affection for childhood friend Takaaki, who remains hospitalized long-term with a heart condition.

Initially confused by her powers, Miyako adapts to superhero responsibilities. She receives paternal mentorship from Professor Utonium and engages in dynamic teamwork with Powerpuff Girls Z allies Momoko Akatsutsumi (Hyper Blossom) and Kaoru Matsubara (Powered Buttercup). Bonding with Momoko over fashion trends contrasts with navigating trio conflicts stemming from their differing personalities.

Juggling adolescent life, Miyako covertly leaves school obligations for hero duties. Her growth unfolds through battles against monsters born from black Chemical Z rays, evolving into teamwork-focused arcs confronting escalating threats like Him's resurrection.