Hiro Hayami's childhood in Tokyo was marked by poverty. Sent to a church in Amakusa, Kumamoto Prefecture shortly after birth, he was raised affectionately by caretakers until their accidental deaths forced him through multiple child institutions, where he frequently fought. Reunited with his mother in his early teens, they lived in a dilapidated apartment where he discovered Prism Shows through her phone, developing admiration for Prism King Hijiri Himuro. Kou Norizuki noticed his potential and offered an Edel Rose Academy scholarship, accepted by his mother.

At Edel Rose, Hiro faced social struggles as peers viewed him as a "teacher's pet" due to his Norizuki ties. At 13, he befriended Kouji Mihama by defending him from bullies. This friendship anchored his early aspirations: He declared he wanted to be a courage-inspiring "hero" rather than Prism King, requesting Kouji write emotionally impactful songs for him. Under Jin Norizuki's strict supervision after Kou's departure, Hiro complied with demands out of perceived debt, culminating in claiming authorship of Kouji's song "Pride" for their "HiroxKoji" unit debut—a betrayal that fractured their friendship when Kouji left Edel Rose.

Jin's influence warped Hiro into a manipulative, self-centered persona. He masked his true self with charm for fans while deceiving others, including manipulating Ito Suzuno to retrieve "Pride" for his solo debut. His obsession with Kouji's songs stemmed from unresolved guilt and a distorted link to their past. Though publicly the "Absolute Idol" (catchphrase: "Absolute Idol, Love N.G"), privately he battled insecurity and self-loathing. Offstage, he displayed calmer deceitfulness and bit objects like glasses or his thumb—a subconscious craving for maternal comfort.

A turning point came when Hiro sought freedom from Jin. He forfeited a Prism battle against Kazuki Nishina after recognizing Kouji's song "Freedom" as a coded reconciliation. Jin's disqualification of Bell Renjoji ignited Hiro's defiance: During a performance, he exposed Jin's manipulations, confessed his lies to fans, and apologized to Kouji. This led to his resignation from Edel Rose and brief Prism Show retirement, halted by Kazuki and Kouji's insistence on rebuilding trust. They formed the unit Over The Rainbow, symbolizing renewal.

Later, Hiro supported Kouji's move to America but faced setbacks when Schwarz Rose claimed rights to "Pride." Resolved to honor Hijiri's legacy, he pursued the Prism King title. His dependency on Kouji's songs resurged, causing a slump after losing a duel to Kouji in America. Encouraged by Edel Rose juniors like Yu Suzuno—who composed a replacement song—Hiro performed "Pride" at the Prism King Cup despite legal risks. Kakeru Juuouin restored the song's rights, and Hiro's performance earned him the Prism King crown with the Prism Goddess's blessing, cementing his growth as an independent performer.

Beyond performing, Hiro modeled in commercials and acted in films like "Yoru no Yoshaman." His fan symbol remained the yellow rose, reflecting his idol identity. His journey emphasized reconciling past trauma with his role inspiring others.