Ichie Ono is a central figure in the narrative, serving as the primary catalyst for the story's events. She is a student at Daikoku Welfare Academy, a boarding school in a future Japan where children are the nation's most precious and closely monitored resource. Ono is the closest friend of Shiori Fuyumura. Before the story begins, Ono is officially declared missing, and after six months without a trace, she is presumed dead, a conclusion that her friend Fuyumura refuses to accept. This disappearance is the great mystery that sets the plot in motion, as Fuyumura’s desperate search for her leads to the discovery of Kazushige Sanda’s true identity as a descendant of Santa Claus.

Ono is portrayed as a thoughtful and somewhat rebellious individual. Described as an avid reader, she was the type of person who questioned the purpose of rules she found absurd and desired to do things that were forbidden. This rebellious spirit is contextualized by the oppressive nature of her society, which prioritizes controlling children’s development above all else. Her skepticism of these norms proves to be justified given the dystopian reality of her world. Furthermore, Ono is one of the few people who still believes in the legend of Christmas and Santa Claus, a concept that has become a forgotten fairy tale for most of her generation.

Her core motivation, which drives the entire conflict of the series, is a desire to avoid a specific, perilous fate. It is later revealed that Ono did not simply vanish but instead went into hiding. She entered a state of seclusion after she unexpectedly hit puberty, a natural biological event that carries extreme danger within the academy’s system. The headmaster of the academy, Hifumi Oshibu, targets children who reach this stage of development, making Ono a marked individual and forcing her to disappear to protect herself.

The most significant and defining relationship for Ichie Ono is her bond with Shiori Fuyumura. They are described as best friends, but the depth of Ono’s feelings is more profound, as she secretly harbors romantic love for Fuyumura. This unspoken affection adds an emotional layer to her disappearance, transforming Fuyumura’s search from a quest to find a missing friend into a desperate, even violent pursuit. It is Fuyumura’s profound connection to Ono that drives her to attack Sanda and threaten her classmates with dynamite, all in the hope that Santa Claus’s power can locate the missing girl who means everything to her.

In terms of narrative role, Ichie Ono functions as the structural backbone of the story. She is the axis of information and the first motive for the entire plot, representing the central mystery that the protagonists are determined to solve. Her absence is a constant pressure on the main characters, and the conspiracy surrounding her disappearance unravels a much more complex and dangerous panorama of the world they inhabit. As the characters get closer to finding her, they uncover secrets that threaten the very fabric of their society.

While not a prominent combatant, Ono possesses a notable and subtle ability for stealth and freedom of movement. Even while missing, she appears to have a certain amount of liberty to walk around the school unseen when nobody is watching her, suggesting a resourcefulness and knowledge of the academy’s hidden corners. Her development is revealed through the circumstances of her disappearance; she transitions from a presumed victim to an active agent who chooses to go into seclusion to survive, all while carrying the secret of her feelings for Fuyumura.