Hiroshi Nonomura, stepbrother to Ami Nonomura, shares a bond that drives their story’s core. After attending junior high together in Japan, their childhood closeness spiraled into a clandestine romance uncovered by their mother, prompting Hiroshi’s abrupt relocation to London for studies—a strategic separation to dismantle their affair.

While abroad, Hiroshi clung to a tangled emotional connection with Ami. He later returned to Japan, resolving to sever their relationship publicly, citing societal expectations and family duty. This choice fractured Ami emotionally, fueling her later struggles. Before leaving again, he discreetly abandoned a book in his room: *First Love*, housing a photo of Ami and a cryptic note—"If Ami weren’t my sister…"—exposing his unresolved longing and the guilt underpinning his pragmatic decision.

Hiroshi’s physical absence and the emotional vacuum left by their fractured bond deeply influenced Ami’s path. Her identity crises and fraught relationships echoed his shadow, culminating in her choice to pursue adulthood by traveling to London—a mirror of his exile and an attempt to confront their fractured history. Their relationship, woven with secrecy and cultural taboo, became a lens for themes of illicit love and the weight of familial responsibility.

Hiroshi remains an enigmatic force in Ami’s life, his legacy defined by catalyzing her emotional evolution and the enduring echoes of their forbidden ties.