Hinoki Otoha is introduced as a senior and a rival to the protagonist, Tonbo Oi. She is a fellow student at the Musashizuka Golf Practice Range, placing her within the same training environment as Tonbo. Hinoki is depicted as a highly talented junior golfer, having won the Kyushu women's tournament two years prior to her main appearance in the story. She is keenly aware of her competition and views Tsubura Adaniya, the tournament winner from the previous year, as her primary rival.

Personality-wise, Hinoki is described as earnest and kind by nature. However, her character is deeply affected by the significant pressure she faces from her father, who holds very high expectations for her success in golf. This pressure becomes a central motivation for her actions, creating an internal conflict between her natural disposition and the overwhelming need to meet external demands.

In her role within the story, Hinoki serves as one of Tonbo's initial rivals when the narrative moves to Kumamoto Prefecture. Her path crosses with Tonbo on the golf course, where their contrasting approaches to the game lead to a shift in Hinoki's perspective as she witnesses Tonbo's bold and carefree playing style. The most significant moment in her character development occurs when the pressure from her father drives her to cheat during a match. However, in a demonstration of her underlying integrity, she finds the courage to confess her dishonesty before the awards ceremony. This act of admitting her mistake is a pivotal point of growth for her. Her notable abilities on the golf course are clear, as she is recognized as a talented player who has already achieved success by winning a regional championship.