Chiyu Tamade, known as CHU², is a 14-year-old third-year high school student at Celosia International School, accelerated nearly three years due to exceptional academic performance. Born into a wealthy, musically prominent family, her mother is the world-renowned violinist Miu Tamade. Pressured from early childhood to master piano and violin and enter competitions, she faced harsh criticism highlighting perceived inadequacies against family expectations. This fueled deep-seated insecurity and a drive to prove herself, leading her to abandon instrumental performance for music production using DTM software. Her ambition solidified into creating "the ultimate band," RAISE A SUILEN (RAS), after Roselia's vocalist Yukina Minato rejected her production offer, an event she interpreted as personal humiliation. Initially, CHU² led RAS with controlling and antagonistic behavior, viewing members as tools to crush Roselia and later Poppin'Party. She forbade interactions with rival bands and imposed strict demands. Her arrogance and short temper caused frequent conflicts, culminating in a breakdown after RAS temporarily lost to Roselia, where she insulted keyboardist Reona Nyubara (PAREO) and drove members away. This dissolved the band and isolated her. Hiding in her penthouse closet, she reflected on her motivations. Bassist Rei Wakana (LAYER) intervened, prompting CHU² to seek out Reona in Kamogawa and offer a sincere apology, acknowledging her flaws and envy of the others' talents. This reconciliation marked her redemption, shifting her focus from rivalry to mutual respect with Roselia and Poppin'Party, though she retains a competitive streak, occasionally issuing playful challenges like attempting to out-eat rivals. CHU²'s personality blends professionalism and confidence with emotional fragility. She self-identifies as a "kind, generous producer" but struggles with outbursts, later expressing regret for harsh words. Her international schooling leads to frequent English code-switching and referring to herself in katakana as "ワタシ" (watashi). She is meticulous in music production, often skipping meals or sleeping under her desk during intensive sessions. Physically, she stands at 140 cm tall with salmon-pink hair, blue eyes, and a distinctive ahoge. She consistently wears black cat-ear headphones and her Celosia uniform—a dark blue blazer, plaid miniskirt, striped tie, and loafers—though her 6th-anniversary casual attire is a turquoise tank top with a white jacket. She prefers jerky and meat snacks, dislikes salads without dressing, avoids baths in favor of showers, and is sensitive to extreme temperatures. Her penthouse serves as both RAS's practice space and studio, reflecting her family's wealth. The stage name CHU² derives from the katakana for her first name "チユ" (Chiyu), stylized with a superscript "2". Her given name's characters mean "to know" (知) and "reason" (由); her surname combines "jewel" (珠) and "hand" (手).