Yu Takasaki attends Nijigasaki High School in Odaiba, Tokyo, as a second-year student. She shares an apartment building with her childhood friend Ayumu Uehara, and they belong to the same class. Her passion for school idols ignited after witnessing Setsuna Yuki’s performance, driving her to join Nijigasaki’s School Idol Club alongside Ayumu.

Unlike performing members, Yu serves as the club’s manager and support figure, coordinating activities and offering emotional encouragement. Over time, she expands her role to become the group’s lyricist and composer, demonstrating musical talent. She practices piano diligently, achieving proficiency and creating original songs like "Yume ga Koko Kara Hajimaru yo." Her intense dedication to music occasionally distracts her from academic responsibilities.

Insightful, reliable, and proactive, Yu exhibits strong empathy and bonds easily with others. Her charismatic nature attracts peers, while her enthusiasm for school idols fuels her commitment to helping members achieve individual goals. She frequently exclaims her catchphrase, "I'm thrilled!" Her development includes transferring from the general curriculum to the music course, reflecting her deepening dedication to musical creation.

Physically, Yu has medium-length black hair with green-dyed tips styled in twin-tails, green eyes, and stands 156 cm tall. She typically wears black thigh-high socks as part of her uniform. Her designated image color is black (#1d1d1d), symbolizing her supportive role.

Her surname "Takasaki" combines the kanji for "tall" (高) and "blossom" (咲), forming a fictional surname. Fans voted to select her given name "Yu" (侑). Before her official naming, she was nicknamed "Anata" (あなた), meaning "you," reflecting her origins as a player-insert character in Love Live! School Idol Festival ALL STARS. She lacks official statistics like birthdate or blood type, though some fans unofficially designate January 29 as her birthday.