Masato Hijirikawa, eldest son and heir to the Hijirikawa Group financial empire, grew up in Kyoto's strict, traditional environment. His upbringing emphasized duty and conformity, forging a reserved, serious, and initially stoic demeanor. Childhood warmth was absent, as interactions with his father focused solely on corporate succession, creating isolation. He found solace in music after the family butler taught him piano, providing emotional release. His decision to pursue idol training at Saotome Academy defied his father, leading to a compromise: one year at the academy before returning to family obligations.

A snowy-day encounter with Haruka Nanami singing joyfully with children in a park became pivotal. Her passion for music inspired his idol path and solidified his resolve to attend Saotome Academy despite opposition. This moment forged a deep, unspoken connection to Haruka long before their formal meeting.

Though outwardly calm and unflappable, Masato harbors complexity. His upbringing makes vulnerability difficult, often rendering him rigid or old-fashioned. Yet he possesses quiet determination and deep sensitivity, especially toward music and cherished individuals. Key traits include intense perfectionism, profound responsibility, and a hidden playful side reserved for trusted companions. He fears insects and dislikes milk despite drinking it for health. His hobbies—calligraphy, sewing, and embroidery—were learned to support his frail mother; he crafts handmade gifts for his treasured younger sister, Mai.

His relationship with roommate Ren Jinguji, fellow heir to the Jinguji Group dynasty, stems from a fractured childhood friendship strained by familial expectations. Their fierce rivalry springs from mutual envy: Masato resents Ren's perceived freedom as a youngest son, while Ren covets Masato's inheritance rights. Clashes in values, particularly Ren's initial dismissal of music's importance, trigger physical confrontations. Despite this, they share profound mutual respect. When Masato faces paternal pressure to abandon his idol career, Ren offers steadfast support, revealing their underlying bond.

Masato's growth centers on embracing personal desires over familial duty. Initially passive about his predetermined future, Saotome Academy experiences—especially collaborations with Haruka—empower him to assert his identity. Key milestones include helping Haruka overcome piano performance anxiety (mirroring his emotional opening), publicly defying his father at a cultural festival to declare his musical commitment, and renegotiating family ties after his father's illness. By *Legend Star*, he actively balances heritage with artistic ambitions, demonstrating heightened confidence and resilience.

His musical evolution parallels personal growth. Early compositions reflect restrained emotions, but performances gain passion as he channels experiences into art. The song "Knocking on the Mind" embodies his feelings for Haruka and symbolizes his journey toward emotional honesty. Piano remains his primary instrument, with performances noted for technical precision and evolving tenderness.

Mai, his younger sister, motivates his desire to protect innocence and ensure she experiences greater freedom than he did. He frequently creates embroidered gifts for her and prioritizes her well-being in personal decisions.