Hitomiko Kira is introduced as the new coach for Raimon Eleven during the team's battle against Aliea Academy, replacing the previous coach who had to leave for another assignment. Her appointment marks a significant change in leadership style, as she presents herself with a calm, cool, and often stern demeanor that stands in stark contrast to her predecessor. Physically, she is depicted as a tall woman with long black hair and large blue-grey eyes. Her typical attire consists of a light yellow jacket over a blue shirt paired with orange trousers. In later appearances, her appearance matures slightly, and she begins wearing glasses.

Her personality at first glance appears cold, strict, and somewhat distant. She is a woman of few words who rarely explains her decisions, issuing commands and strategies that often seem baffling or even cruel to the players. This is most notably demonstrated by her immediate and seemingly heartless decision to remove the team's star forward, Shuya Goenji, from the roster. However, this frosty exterior is a carefully constructed facade. Her true nature is deeply compassionate and kind-hearted. Her harsh methods and enigmatic orders were always part of a calculated plan to make Raimon the strongest team on earth and, more importantly, to put a stop to her own father's sinister ambitions. The decision to force Goenji to leave the team, for example, was later revealed to be a measure to protect his younger sister from being used as a hostage by Aliea Academy.

Hitomiko's personal history is deeply intertwined with the plot she steps into. Years before the events of the series, her biological younger brother, Hiroto Kira, died in an accident. To help her grieving father, Seijirou Kira, she suggested he create an orphanage called Sun Garden to care for other children who had lost their families. They both came to care for these children, with Hitomiko seeing them as her own siblings. However, tragedy struck again. Seijirou discovered the Aliea Meteorite, a strange mineral that vastly enhanced soccer abilities but also corrupted its users, making them ruthless and aggressive. Consumed by a desire for revenge over his son's death and for power, Hitomiko's father used the meteorite on the children of Sun Garden, turning them into his personal soldiers to form the various teams of Aliea Academy. When her pleas to stop this project failed, Hitomiko entered the world of soccer with the goal of using Raimon to stop her father and save the children who had become his pawns.

In her role as coach, Hitomiko proves to be exceptionally talented from a tactical and technical standpoint. Her greatest strength is her ability to analyze a player's capabilities and determine the most effective position for them, often moving players to entirely new roles on the field, a practice known as libero. She famously moved Mamoru Endo from his trusted position as goalkeeper to a libero role, a change that ultimately strengthened the team. Her strategies are well-thought-out and designed to counter the specific threats posed by the powerful and brutal Aliea teams, even if her methods for achieving this growth put immense pressure on her players. While her strategic mind is sharp, her management of the players' emotional and psychological well-being is often questioned. Her focus on results and tough love pushed some members, like Kazemaru and Kurimatsu, to their breaking point, leading to them temporarily leaving the team. She plays a critical role in the story, guiding Raimon through battles against teams like Gemini Storm, Epsilon, and finally The Genesis. It is during the climactic battle against The Genesis that her secret is fully exposed when the opposing captain, Hiroto Kiyama, who she raised in the orphanage, calls her sister.

Key relationships define her journey. Her relationship with her father, Seijirou Kira, is the central conflict that drives her actions. She loves him but is forced to oppose him to stop his destructive plan. Her bond with the children from Sun Garden, especially Hiroto Kiyama, is that of a protective older sister, and she works to free them from their father's control. Her relationship with the Raimon players evolves significantly over time, starting from a foundation of mistrust and confusion to one of deep respect and gratitude as they come to understand her true intentions.

Throughout the series, Hitomiko undergoes a clear development. The cold, unreadable coach of the Aliea Academy arc is revealed to be a woman carrying a tremendous burden of guilt and responsibility. After Aliea Academy is defeated and the conflict is resolved, she sheds her harsh persona. She shows her caring nature by accepting a request from a former adversary to form and coach a new team called Neo Japan, giving them a chance to prove themselves for a spot on the national team. In the Inazuma Eleven GO series, several years later, Hitomiko is seen as the kind and gentle caretaker of the Sun Garden orphanage, now free from her father’s shadow. Her appearance has changed only slightly with the addition of glasses, and she continues to watch over and nurture the next generation of children, including a talented player she later entrusts to Endo's care. Her tactical abilities remain formidable, but her interpersonal skills have softened significantly, completing her transformation from a secretive agent to a supportive maternal figure.