Hiroko Makunouchi is the mother of the protagonist, Ippo Makunouchi, and the owner and operator of the Makunouchi Fishing Boat business in Tokyo, Japan. Her background is marked by profound loss, as her husband, Kazuo Makunouchi, was a commercial fisherman who was declared lost at sea and later presumed dead after sacrificing himself to save a crewmate during a storm. Following this tragedy, Hiroko was determined to continue her husband's dream of running a fishing charter business. With the help of the local fishermen her husband had worked with, she earned her captain's license after three attempts and established the family business that serves as the central setting for much of her son's early life.

In terms of personality, Hiroko is characterized as a kind, strong-willed, and deeply caring individual. She possesses a quiet but immense inner strength, having shouldered the responsibility of raising her son and running a business alone for many years. Her primary motivation is the well-being and future of her son, Ippo. She works tirelessly at the fishing boat, often to the point of exhaustion, to provide for him and ensure he has opportunities she did not want him to sacrifice. A defining aspect of her personality is her stance on boxing: she refuses to attend any of Ippo's matches because she cannot bear to watch him be hurt. However, she supports his passion for the sport wholeheartedly, recognizing the joy, confidence, and purpose it has brought to his life. Her love is shown through practical support, such as preparing large meals for him before fights and allowing him to leave for training camps, despite her personal anxieties.

Hiroko's role in the story is primarily as a source of emotional grounding and motivation for Ippo. Her hard work and sacrifices are a major reason Ippo considers quitting boxing at several points, as he feels a deep filial responsibility to help her and take over the family business. Her health is a recurring plot point, as her tendency to overwork herself leads to hospitalization, which directly conflicts with Ippo's boxing career. The resolution of one such conflict, when Ippo's former bully Masahiko Umezawa begins working at the boat to allow Ippo to continue boxing, highlights her role in the community and her capacity for forgiveness. Her key relationships are with her son, who she considers her reason for never being truly alone, and with her late husband, whose memory she continues to honor. She also shares a significant bond with Umezawa, whose efforts she silently acknowledges, and with other members of the Kamogawa gym who occasionally visit the fishing boat.

Regarding development, Hiroko evolves from a grieving widow struggling to manage a new business to a capable and resilient proprietor. Her personal journey includes a quiet acceptance of her son's chosen path in boxing. While she never overcomes her aversion to watching him fight, she moves from seeing boxing as a source of injury to understanding it as an important adventure for her son, one where he can face hardships, fall down, and rise again. In a significant moment, she contrasts her late husband, a strong fisherman who saved others, with her son, acknowledging that Ippo possesses a different kind of strength as a second, guiding other athletes. Her notable abilities are not physical but rather her unwavering work ethic, her ability to manage a small business, and her profound emotional resilience and perceptiveness. She has the ability to see through her son's attempts to hide his tears and is attuned to his needs, offering advice such as suggesting he visualize his opponent as a fish, a tactic he learned from his father. Her strength lies in her quiet, steadfast love and the stable home and livelihood she provides, which serve as the foundation for Ippo's entire journey.