Otoya Ittoki is a bright-eyed Saotome Academy student with vivid red hair, standing 175 cm tall with an athletic frame. Initially placed in Class A, his life began with profound loss: his biological mother vanished in a plane crash during his infancy, leading him to be raised by a maternal aunt. After his aunt succumbed to poor health, he spent his childhood in an orphanage, forging a deep-seated fear of abandonment. This fear drives him to mask his emotional pain behind a perpetually cheerful smile, haunted by the conviction that others would reject his true vulnerabilities. A later revelation identifies academy chairman Shining Saotome as his biological father and Cecil Aijima as his maternal half-brother.

Naturally kind and energetically optimistic, Otoya possesses a genuine love for music and innate athleticism, excelling in dance, soccer, and acrobatic agility. He forms bonds easily, offering unwavering support to friends like Haruka Nanami, whom he assists during her entrance exam and defends from bullies. His empathy extends to frequent visits to his childhood orphanage, where he organizes events and performs uplifting songs like "SMILE MAGIC" for the children. Despite his outwardly carefree nature, he grapples with insecurities about his musical abilities and anxieties rooted in his past.

His journey at Saotome Academy charts significant growth. As a first-year, he partners with Haruka for recording tests, co-writing "BRAND NEW MELODY" inspired by her humming. Joining the group ST☆RISH, he contributes lyrics to songs like "Maji LOVE 1000%" and "Mirai Chizu," and demonstrates loyalty by mediating conflicts, such as reconciling with Tokiya Ichinose after Tokiya's secret identity as HAYATO surfaces. Progressing to the Master Course, he mentors under Reiji Kotobuki and showcases comedic improvisation on variety shows. A pivotal duet project with senior idol Eiichi Ōtori forces a confrontation with his traumatic past, triggering a psychological crisis. Under Eiichi's influence, he withdraws emotionally, adopting a hollow "true self" persona, highlighting his struggle to reconcile his history with his idol identity.

Relationships are central to his narrative. He shares mutual respect and unspoken romantic feelings with Haruka, nearly confessing multiple times but retreating due to the academy's romance ban. Rooming with Tokiya, their relationship evolves from initial intimidation to steadfast camaraderie, with Otoya often defending him. Within ST☆RISH, he collaborates closely with members like Natsuki Shinomiya and Syo Kurusu, while his familial bond with Cecil adds complexity. Musically specializing in guitar, he contributes to numerous songs, including "TRUST☆MY DREAM," "Over the Rainbow," and the duet "NEXT DOOR" with Eiichi. His singing style emphasizes upbeat, heartfelt melodies, reflecting his optimistic persona.