Yū Takasaki is a second-year Nijigasaki High School student who founded the School Idol Club, acting as its manager and later becoming an honorary school idol. She resides near Odaiba and has been inseparable childhood friends with Ayumu Uehara since early childhood, sharing the same school and class. Witnessing a performance by Setsuna Yuki sparked her passion for school idols, leading her and Ayumu to join Nijigasaki's club. Known for her insight, reliability, empathy, and sociability, she possesses a deep dedication to supporting school idols. Her charismatic and proactive nature fosters strong bonds, though her intense focus on music sometimes results in neglected schoolwork. Physically, she has medium-length black hair with green-dyed tips styled in twin-tails, green eyes, and often wears black thigh-high socks. Her height is 156 cm (5'1"). Her designated image color is black, symbolizing her supportive role rather than performance. Her involvement evolves significantly. Initially centered on club management and logistics, she progressively develops musical skills, particularly piano. Early displays like a brief piano performance in "Shout Out Your Love" show basic ability, while later scenes in "Summer Begins" and "Blossoming Feelings" demonstrate advanced proficiency. Her compositional talent emerges when she plays a snippet of "Yume ga Koko Kara Hajimaru yo" in "Blossoming Feelings," later confirmed as a full song in "School Idol Festival (The Place Where Everyone's Dreams Come True)," aligning with her game role as the club's primary songwriter. In the "Final Chapter" film trilogy's Part 1 (September 2024), her screen time is minimal, primarily showing supportive interactions with Ayumu. Her role in the unreleased Part 2 ("Kanketsu-hen Dai-2-Shō," scheduled November 2025) has no concrete details. Her surname, Takasaki (高咲), combines "tall/high" (高) and "blossom" (咲), and is fictional. The kanji for her given name, Yu (侑), meaning "to urge to eat," was chosen by a fan to reflect her supportive nature. Before her official naming, she was nicknamed "Anata" (あなた, "You"), leading to fan references treating her as a self-insert character. She lacks official statistics like birth date or blood type, unlike other club members; fans unofficially celebrate her birthday on January 29. She occasionally wore a shirt with the character "Pa" (ぱ) during childhood, differing from other protagonists who wore name initials.