Amamiya Hikari is a central figure in the story of H2: Kimi to Ita Hibi, known as the childhood friend of the protagonist Hiro Kunimi and the girlfriend of his best friend, Hideo Tachibana. Her birthday is August 16. She is portrayed as a beautiful, bright, and popular young woman who often carries herself with a sense of maturity and level-headedness that sets her apart. Her personality is noted for being both generous and delicate, often using jokes and a teasing manner to mask her true feelings, which frequently places her at the center of the story's emotional tensions.

From a young age, Hikari shared a deep bond with Hiro, growing up alongside him as a close neighbor and confidante. In their middle school years, Hiro, who was still immature and uninterested in romance, acted as a matchmaker, introducing Hikari to Hideo and facilitating the start of their relationship. It was only later that both Hikari and Hiro realized their feelings for one another had evolved beyond a familial or platonic sibling-like affection, creating a complex and unresolved emotional undercurrent. Her motivations are largely driven by a desire to maintain harmony between the two most important people in her life, Hiro and Hideo, while struggling with her own conflicting loyalties and emotions. She carries the significant emotional pressure of this triangle, often shouldering the burden to avoid hurting either of them.

Within the story, Hikari serves as a crucial emotional anchor and a source of inspiration. She is a constant supporter of both Hiro and Hideo's baseball ambitions, having been a steadfast spectator of their exploits since their undefeated championship days in middle school. As a student, she is a member of the archery club. However, her role expands when, at Hideo's request, she temporarily serves as the manager for the prestigious Meiwa Daiichi High School baseball team during their tournament run at Koshien. This position puts her at the heart of the baseball world that separates her from Hiro. Her aspirations extend beyond high school, as she dreams of becoming a journalist.

Hikari's key relationships define her character arc. Her relationship with Hideo is outwardly stable and committed, yet it is challenged by the unspoken history she shares with Hiro. Conversely, her bond with Hiro is one of profound familiarity and unspoken understanding, marked by shared history and moments of vulnerability that she cannot experience with anyone else. This is most evident after the death of her mother, a devastating event that leaves Hideo unable to comfort her fully; she is only able to truly cry and grieve in Hiro's presence. Throughout the series, Hikari undergoes significant development, moving from a girl who passively accepts the path set for her to someone who actively confronts her own emotions. The narrative forces her to the crossroads of her feelings, culminating in the summer tournament where Hideo gives her an ultimatum to choose between him and Hiro. In the end, following the climactic semi-final game between Senkawa and Meiwa Daiichi, Hikari reconciles with Hideo, who admits his need for her after his defeat. While she chooses to remain with Hideo, her true feelings are laid bare, marking a poignant resolution where she acknowledges her love for Hiro but accepts the reality of her choices. Her notable ability, beyond her skill in archery, is her profound emotional intelligence and her capacity to understand the hearts of both Hiro and Hideo, even when they struggle to understand themselves.