An Shiraishi assists her father, former musician Ken Shiraishi, at his live cafe and bar, WEEKEND GARAGE. Immersed in music from childhood and inspired by her father's legacy, she naturally connects with singing. Her ambition is to surpass the legendary RAD WEEKEND event, originally organized by her father's team. This goal faltered briefly upon learning a significant secret about her role model, Nagi (Ken's former teammate), but after understanding Nagi's aspirations through Ken, An recommitted to exceeding RAD WEEKEND. Her cheerful, honest, and unyielding personality leaves strong impressions. She exhibits candid affection towards close friends but feels nervous enforcing rules as part of Kamiyama High School's disciplinary committee. Growing up in WEEKEND GARAGE grants her broad connections within Shibuya's street music scene. She has amber eyes and long black hair with blue tips, usually worn loose; star accessories are removed during school. Casual wear includes a light gray crop top, black athletic undershirt, and high-waisted denim pants. Her performance outfit features a teal-and-white oversized jacket, white shorts with neon accents, and chunky headphones. After seeing Kohane Azusawa's reaction to her singing at WEEKEND GARAGE, An invited Kohane to form the duo Vivids. Through rivalry and collaboration, they later united with former competitors Shinonome Akito and Aoyagi Toya to create Vivid BAD SQUAD, though Vivids remains active. An initially showed overprotectiveness towards Kohane, later developing feelings of inferiority regarding Kohane's rapid vocal improvement and fearing being surpassed. An confessed these anxieties about being left behind, strengthening their partnership. Their closeness is such that others immediately associate An's social plans with Kohane. An shares a longstanding rivalry with Akito since middle school, evolving from distance and animosity into friendly competition and blunt banter within Vivid BAD SQUAD, driving their growth. Mutual respect developed gradually with Toya after the unit's formation, with An offering relatable support during his challenges. At school, her classmates include first-year Akiyama Mizuki and second-years Akito and Kusanagi Nene. An deepened her friendship with Nene through collaborative film work during the "Picture Perfect!" event, praising Nene's directing skills. She maintains a childhood friendship with Kiritani Haruka from elementary school, despite attending different high schools, reflected in their "Rivals in Everything but Studying" Trust Rank title. An admires Hinomori Shizuku, initially knowing her as an idol and becoming flustered during close interactions, clarifying this as admiration. Other connections include friendship with Hanasato Minori through Kohane, camaraderie with Shinonome Ena (learned about from Akito), and supportive interactions with Hinomori Shiho after meeting during the "Scramble Fan Festival!" event. During the film's events, An participates with Vivid BAD SQUAD when the mysterious Miku transports all five musical groups into her collapsing SEKAI. She contributes to the collective effort to restore hope through music, performing "Fire Dance" with her unit to reconnect Miku with her audience.