Mia Iriomote is a 26-year-old singer who performs under the name MIA. She has built a substantial social media following, with over 100,000 followers on Instagram, and is known for her confident, self-assured public image. Despite her popularity, Mia tends to prioritize her physical fitness and online presence over refining her vocal technique, a trait that makes her both a formidable and flawed opponent.

In the story, Mia serves as an early obstacle for the protagonist, Eiko Tsukimi, who admires Mia's success but is intimidated by the challenge of competing against her. Mia's arrogance stems from her reliance on her existing fan base rather than genuine artistic growth, yet even the strategist Kongming acknowledges her raw talent. She rides a motorcycle and carries herself with a brash, independent attitude that reflects her belief in self-promotion over pure musicality.

Her key relationship is with Eiko, whom she views as a rival; their dynamic pushes Eiko to confront the gap between amateur passion and commercial success. Mia's character development is limited, as she remains a representation of the entertainment industry's superficial side—a talented singer who coasts on popularity rather than striving for excellence. Her notable abilities include a strong stage presence and an intuitive grasp of social media engagement, but her lack of vocal dedication makes her a cautionary figure within the narrative. In the movie, she appears as one of the many artists participating in the massive music battle festival, maintaining her role as a popular but complacent singer who must adapt when faced with genuine competition.