Ai Hoshino endured a childhood scarred by domestic violence inflicted by her mother. Following her mother's arrest for theft, Ai entered an orphanage. Her mother, upon release, never reclaimed her, leaving Ai to grow up institutionalized. This upbringing rendered her incapable of understanding or feeling love, convinced she was undeserving of affection. At twelve, Strawberry Productions president Ichigo Saitou scouted her for an idol career. Hesitant due to her emotional limitations, Ai agreed after Saitou reframed lying as an acceptable, even desirable idol trait, persuading her that false expressions of love could eventually turn genuine. This belief became central to her identity.

Ai ascended to stardom as the center member and face of idol group B-Komachi. Her unique charisma and captivating stage presence drew intense audience focus during performances. Colleagues and observers deemed her a rare talent unlikely to be seen again. At sixteen, she became pregnant with twins after a secret relationship with Hikaru Kamiki. Despite the significant career risk inherent in the image-controlled idol industry, she chose to carry the pregnancy to term and raise the children secretly, driven by a deep-seated desire for the familial love she had always craved. She named her children Aquamarine and Ruby.

Balancing motherhood with idolhood demanded extreme secrecy. Ai compartmentalized her life, hiding the twins from the public and colleagues. She maintained her demanding performance schedule while caring for her children privately. Offstage, her personality contrasted sharply with her idol persona; she was described as asocial, with few close friendships, primarily maintaining industry connections. Observers noted traits of impulsiveness, recklessness, and disorganization, attributed to her abusive upbringing and lack of formal education. Her demeanor shifted after meeting her boyfriend, becoming more cheerful, feminine, and less self-destructive.

Ai's complex relationship with truth defined her. She viewed lies told to fans as a form of love, believing insincere expressions could evolve into genuine emotion. This philosophy extended to motherhood; though cherishing her time with Aquamarine and Ruby, she never verbally expressed love, fearing the words might be false. This internal conflict persisted.

Ai was murdered at twenty by Ryosuke Sugano, an obsessive fan. Sugano, manipulated by Hikaru Kamiki (who leaked her location), attacked her at home, stabbing her in front of her children. Dying, Ai recognized Sugano from fan meetings and recalled a trinket he'd given her, causing him to flee in distress before later taking his own life. With her last breaths, Ai told Aquamarine and Ruby she loved them, finally acknowledging her genuine feelings. Her death catalyzed her children's paths: Ruby pursued idolhood to emulate her mother, while Aquamarine dedicated himself to uncovering the truth behind her murder and seeking revenge.

Before her death, Ai recorded two DVDs for her children, entrusted to director Taishi Gotanda for delivery upon their eighteenth birthdays, suggesting possible foreknowledge. Her legacy continued to influence events long after her passing, her children grappling with her absence and the weight of her choices. Her distinctive physical traits—gradient purple-to-pink eyes each featuring a six-pointed star—were inherited by her children, though each possessed only one star. These stars symbolized her dual struggles: one representing the deception of her idol persona, the other her internal conflict over motherhood and authentic love.