Nana Komatsu, frequently referred to by the nickname Hachi, is a central character in the anime NANA. She is a twenty-year-old woman from an upper-middle-class background who moves to Tokyo in search of love and a fresh start. Her nickname Hachi, bestowed upon her by Nana Osaki, is derived from the legendary loyal dog Hachiko and reflects her earnest, faithful, and affectionate nature. She is cheerful, optimistic, and deeply romantic, often driven by a powerful desire to be loved and to make those around her happy. This eagerness to please can lead her to seek validation through romantic relationships and to adapt her own identity to fit the expectations of others, sometimes resulting in a loss of self-direction. She struggles with indecisiveness and a tendency to drift with circumstances rather than making firm choices, yet she is also remarkably resilient and empathetic, capable of finding good in difficult situations and forgiving others repeatedly. Her primary motivations are to find a stable loving relationship, build a family, and support her friends' aspirations, often placing the needs of her loved ones before her own.

Within the storyline, Hachi serves as a poignant counterpart to her best friend and former roommate, Nana Osaki. Their friendship is a foundational relationship that shapes much of her emotional growth. While Osaki embodies independence and professional ambition, Hachi represents hope, romance, and the vulnerability of seeking connection. Her key relationships include her marriage to Takumi Ichinose, a complex union catalyzed by an unplanned pregnancy, and her feelings for Nobuo Terashima, who personifies her ideal of romance. These relationships force her to navigate the tensions between her desire for security and her need for genuine emotional fulfillment. Through her experiences, Hachi develops from a naive and dependent young woman into a more mature individual who learns to confront difficult choices and bear responsibility. She does not possess supernatural abilities, but her notable strengths include her cooking, which she uses as an expression of care, her profound empathy, and her emotional resilience. She has an extraordinary capacity to remain open-hearted and hopeful even after experiencing heartbreak. Her character arc revolves around learning to balance her innate warmth and need for connection with a stronger sense of self-worth and autonomy, ultimately striving to love deeply without losing herself entirely.