Hinowa, also known as the Sun of Yoshiwara, is the highest-ranking courtesan in the Yoshiwara district, an underground city of pleasure that is permanently sealed from the sun. She is a woman of remarkable inner strength and resilience, whose very presence serves as a beacon of hope in an otherwise hopeless place. Physically, Hinowa is described as a great beauty with black hair, and despite her circumstances, she carries herself with an unshakeable elegance and grace.

Her background is one of tragedy and sacrifice. Sold to Yoshiwara by her parents as a child, she came under the control of Housen, the fearsome Night King who ruled the district. Unlike most, Hinowa's spirit never broke. She famously urged even Housen to appreciate the sun, a concept lost in their sunless world. Her defining act of sacrifice occurred when she attempted to escape with a young boy named Seita. After being caught, she willingly submitted and returned to save the lives of Seita and an elderly man who had helped them. As punishment to ensure she would never try to flee again, Housen severed her Achilles tendons, leaving her unable to walk and confined to a wheelchair.

Personality is where Hinowa truly shines. She is the embodiment of the sun for the women of Yoshiwara, known for her strong, resilient, and optimistic nature. Her eyes, unlike those of the other inhabitants, show no signs of weariness, vulgarity, or worry. Even after her brutal injury, her soul remains unbroken. She is deeply empathetic, warm, and caring, yet also possesses a spontaneous and somewhat airheaded side that emerges after Yoshiwara is liberated. She can be surprisingly forward, ignoring social niceties to help others or ask for favors, revealing a cheerful and sometimes mischievous personality that had been suppressed under Housen's tyranny.

Her role in the story is pivotal as the symbolic and spiritual heart of Yoshiwara. She is the reason the other courtesans endure, and her presence is the catalyst for the Yoshiwara in Flames arc. It is the desire to rescue her and give Seita a family that drives much of the conflict. After Housen's defeat, she chooses to remain in Yoshiwara, not as a courtesan, but as its new leader. She reopens the district as a more wholesome town and runs a teahouse called the Hinoya, working to create a place that its children need not be ashamed of.

Key relationships define her life. Her most important bond is with Seita, whom she raised as her own son. Although they are not blood-related, Seita is the child of a fellow courtesan who died in childbirth, and Hinowa's love for him is unconditional. Their escape attempt and her subsequent sacrifice were all for his sake. She is also deeply connected to Tsukuyo, the guardian of Yoshiwara. Hinowa served as a mentor and big sister figure to Tsukuyo when she was a child, and in return, Tsukuyo is fiercely loyal and protective of her. Hinowa understands Tsukuyo better than anyone, often seeing through her stoic exterior and gently encouraging her to pursue her own happiness, including her hidden feelings for the protagonist. Her relationship with Housen is complex; while he was her captor and tormentor, he also saw her as the sun he both hated and longed for. In the end, Hinowa showed him compassion in his final moments, forgiving him and understanding his loneliness.

Throughout the series, Hinowa undergoes notable development. Initially portrayed as a tragic, ethereal figure held in a tower, she transforms into an active and pragmatic leader. Once liberated, her character lightens considerably, revealing a more casual, funny, and even slightly devious side as she helps run the new Yoshiwara. While she initially requires a wheelchair, significant rehabilitation over time allows her to eventually stand and walk with the aid of a cane. Despite this progression, her core nature as a source of warmth, resilience, and maternal care remains constant, solidifying her role as the undying sun that illuminates the eternal night of Yoshiwara.