Kanna Endo is first introduced as an infant, the daughter of Kiriko Endo and the niece of the series' original protagonist, Kenji Endo. She is entrusted to Kenji’s care by her mother, which leads to her spending her formative years under the influence of her uncle, an aspiring rock musician who runs a convenience store. This early period is crucial, as Kenji’s kindness, his sense of justice, and his love for rock and roll leave an indelible mark on her, shaping the person she becomes.

As a young woman in the 2010s, following the apocalyptic event known as the Bloody New Year's Eve and the disappearance of her uncle, Kanna emerges as a central figure in the resistance against the authoritarian cult leader known as Friend. She is portrayed as a fiercely independent and charismatic high school student who works part-time at a Chinese restaurant in a neighborhood controlled by rival gangs. Her personality is a direct inheritance of Kenji’s spirit but forged into something more proactive and confrontational. She has a strong will and does not hesitate to stand up for what she believes is right, often placing herself in dangerous situations to protect others. Despite the dystopian world she inhabits, she possesses a warm heart and is deeply loyal to those she considers friends, which inspires fierce loyalty from them in return. This charisma allows her to unite unlikely allies, including warring mafia factions, a feat that highlights her natural leadership abilities.

Kanna’s primary motivation throughout the story is rooted in her relationship with her uncle. She idolizes Kenji and is one of the few people who remains convinced of his innocence after he is posthumously blamed for the Bloody New Year's Eve catastrophe. This belief fuels her desire for justice and her determination to fight against Friend’s oppressive regime, which has rewritten history and taken control of the world. While she leads an underground resistance known as the "Ice Queen," her methods are sometimes seen as reckless, and she struggles with the weight of her role, often feeling insecure about her ability to lead others effectively. Her actions are driven not just by a desire to topple a dictator, but also to clear her uncle’s name and avenge his apparent death.

Her key relationships define her journey. The most significant is the memory of Kenji Endo, whose old cassette tape she clings to as a source of strength and connection. After Kenji’s disappearance, she is raised by Yukiji Setoguchi, a close friend of Kenji’s, who tries to protect Kanna from the dangerous path she is drawn toward. A major turning point in Kanna’s development is the revelation of her biological parentage. She discovers that the masked antagonist, Friend, is her father, a truth that is profoundly devastating and causes her to momentarily lose her sense of purpose. Furthermore, she learns her mother, Kiriko, was a biomedical researcher whose work may have been connected to the Friend's plans. These revelations force her to confront a dark legacy that contrasts sharply with the heroic image she holds of her uncle.

Throughout her arc, Kanna demonstrates notable abilities, the most prominent of which are her low-level psychic powers. She possesses extra-sensory perception, including limited precognition that allows her to guess the outcome of a coin toss or identify which hand holds a hidden object. She is also capable of minor telekinesis, such as bending a spoon with her mind. While these abilities exist, Kanna often dismisses them as largely useless in the grand scheme of her resistance efforts, and she never gains full mastery over them. Her true strengths are her charisma, courage, and the ability to inspire others to action. By the story's end, through trials involving her family secrets and the final confrontation with Friend, Kanna evolves from a girl driven by revenge and the shadow of her uncle into a young woman who finds her own path and a new understanding of justice, culminating in a reunion with her mother in Africa.