"STARMYU" centers around the lives of students at Ayanagi Academy, a prestigious performing arts school known for producing top-tier entertainers. The narrative primarily follows Hoshitani Yuuta, a passionate and determined first-year student who aspires to join the school's elite musical performance group, Team Otori. This group is led by the enigmatic and highly respected third-year student, Otori Itsuki, who serves as both a mentor and an idol figure for many students.

Hoshitani's journey begins when he auditions for Team Otori alongside his friends, Nayuki Toru, Tsukigami Kaito, Kuga Shuu, and Tengenji Kakeru. Each of these characters brings unique talents and personalities to the group, creating a dynamic and diverse ensemble. Nayuki is a skilled pianist with a calm demeanor, Tsukigami is a perfectionist with a strong sense of responsibility, Kuga is a rebellious yet talented dancer, and Tengenji is a former child actor with a refined presence. Together, they form the group "Team Hiragi," named after their homeroom teacher, Hiragi Tsubasa, who guides them through their challenges.

The series explores the rigorous training, intense rivalries, and personal growth of the students as they strive to excel in singing, dancing, and acting. Team Hiragi faces numerous obstacles, including competition from other talented groups like Team Sazanami and Team Yuzuriha, as well as internal conflicts and self-doubt. The students must learn to work together, overcome their individual weaknesses, and prove their worth to earn a place in Team Otori.

Throughout the series, the characters' backstories and motivations are gradually revealed, adding depth to their development. Hoshitani's unwavering determination and optimism inspire those around him, while the other members of Team Hiragi confront their own fears and insecurities. The narrative also delves into the relationships between the students and their mentors, particularly the complex bond between Otori and Hiragi, who share a history that influences their interactions.

The story is structured around various performances and competitions, showcasing the students' growth and the culmination of their hard work. These events serve as milestones in their journey, highlighting their progress and the challenges they must overcome to achieve their dreams. The series balances moments of intense drama with lighthearted camaraderie, creating a compelling and engaging narrative that captures the highs and lows of pursuing a career in the performing arts.