Shuhei Amamiya is born into a wealthy family with a distinguished lineage of pianists. He commences formal piano training at age four, practicing rigorously for hours daily to uphold his family's musical legacy. This upbringing shapes him into a technically proficient virtuoso, though his playing is initially devoid of emotional sensitivity. He views the piano primarily as an inherited obligation rather than a source of personal joy or creative expression.

Upon transferring to Moriwaki Elementary School, Shuhei faces relentless bullying from classmates, leading to a dare involving a supposedly broken piano in the nearby forest. He attempts to play it but fails, unlike his classmate Kai Ichinose, who produces beautiful music effortlessly. This encounter profoundly impacts Shuhei, sparking both admiration and a burgeoning rivalry with Kai. Their shared passion for piano forms the basis of a complex friendship that evolves significantly over time.

Characterized initially by shyness and caution, Shuhei's personality undergoes substantial development through his interactions with Kai. He sheds his reserve, becoming more assertive and willing to take risks. As they mature, Shuhei experiences periods of intense self-doubt, particularly when comparing his own playing to Kai's emotionally resonant performances. Despite this rivalry, he demonstrates deep, albeit often indirect, care for Kai. During a critical performance where Kai struggles, Shuhei uses a deliberate cough to refocus Kai's mind, helping him regain his musical composure.

Physically, Shuhei possesses black hair and brown eyes. His attire consistently reflects his affluent background, appearing well-groomed. In childhood, he wears protective black gloves to safeguard his fingers, emphasizing the disciplined nature of his early piano training.

His journey involves rigorous preparation for piano competitions. While dedicated to technical mastery, he grapples with the pressure of familial expectations, particularly stemming from his father, a renowned pianist who once attempted but failed to replicate the distinctive playing style of Sosuke Ajino, their school's music teacher. This familial history adds another layer to Shuhei's artistic struggles.

Shuhei later moves back to Tokyo yet maintains his connection to Kai. During this period, he encounters Kai cross-dressing as "Maria" while playing piano in a club. Despite the disguise, Shuhei instantly identifies Kai through the distinctive quality of his piano sound, underscoring his deep attunement to Kai's musical identity.

His relationship with Ajino evolves from student-teacher dynamics into one involving mentorship and unresolved legacy, given his father's past connection to Ajino's piano style. Shuhei's mother, Namie Amamiya, is part of his supportive family structure.

Notably, Shuhei's inability to produce sound from the forest piano, unlike Kai, symbolizes their different relationships with music – Shuhei's rooted in tradition and discipline, Kai's in instinctive connection. His return to Tokyo and recognition of Kai in disguise further highlight their enduring, albeit complicated, bond.