Nao Yorihime is a classmate and childhood friend of Haruka and Sora Kasugano, reconnecting when the twins return to their rural hometown after their parents' death. During their shared childhood, frequent arguments between Nao's own parents drove her to seek comfort with Haruka. One such instance, following a family conflict, resulted in her first sexual experience with him. Unbeknownst to them, Sora witnessed this event, significantly altering the future dynamics between the three. Nao later harbors deep guilt over this incident, seeking reconciliation with Sora while desiring to rebuild her relationship with Haruka. Athletic and mature in physique, contrasting with Sora's frailty, Nao stands 1.63 meters tall with black hair, green eyes, and wears glasses. Her blood type is AB. Skilled in sewing—a trait tied to her family's craftsmanship background—she often makes her own clothes and school uniforms. She is also a proficient swimmer. Outwardly cheerful and sociable, Nao easily engages with others, yet this masks deeper insecurities and a tendency to base her self-worth on helping others, sometimes neglecting her own needs. Her demeanor grew withdrawn and apathetic during the twins' absence from the village but rekindled upon their return. She holds longstanding romantic feelings for Haruka, intensifying after their reunion, with her emotional expression including significant, directly portrayed sexual desire towards him. Her narrative arc centers on internal conflict: guilt over her past actions clashes with her persistent romantic aspirations for Haruka. This positions her as an inadvertent disruptor to the twins' relationship. Tensions escalate as Sora perceives her as a threat to her bond with Haruka, leading to confrontations. Nao's efforts to navigate this triangle culminate in Haruka making a definitive choice regarding their relationship and his responsibilities toward Sora.