Yumi Omura is a seventeen-year-old girl who works part-time alongside the protagonist Hideki Motosuwa at a Japanese pub called My Pleasure. She stands approximately 150 centimeters tall with brown hair and brown eyes. In the anime adaptation, she is also the daughter of the establishment's owner, adding a familial connection to her workplace.

Outwardly, Yumi is known for her cute and honest demeanor. She approaches her job with energy and often treats Hideki like an older brother figure, a role he accepts as they navigate their daily lives in the city. Despite her generally bright and cheerful exterior, Yumi harbors deep-seated insecurities, particularly regarding the increasing presence of persocoms, the humanoid computers that populate her world. She struggles with a complex that these machines are, in her view, perfect beings that humans cannot compete with.

This complex forms the core of her personal history and her most significant storyline. Before working at the pub, Yumi was employed at a bakery called Tirol, where she fell deeply in love with the owner, Hiroyasu Ueda. She eventually gathered the courage to confess her feelings and discovered that Ueda reciprocated her affection. However, he also revealed that he was a widower. Driven by curiosity and unease, Yumi investigated her boss’s past and uncovered the tragic truth: Ueda had been married to a persocom whom he had also named Yumi. The persocom had developed a fatal hardware failure, and in her final moments of lucidity, she pushed Ueda out of the path of an oncoming car, sacrificing herself to save his life. Crushed by the revelation that her love was reciprocated but that she shared her name with a "perfect" machine who had performed such a heroic act, Yumi became convinced that Ueda was only interested in her as an inferior substitute for his lost wife. She quit her job at the bakery and began working at the pub in an attempt to move on, though she continued to suffer from the emotional fallout.

Yumi's pain is reignited when Chii, the persocom Hideki found, starts working at the Tirol bakery in a maid uniform that Ueda had specially made for Yumi when she worked there. Yumi witnesses this and runs away in despair, leading to a crucial conversation with Hideki, who chases after her. He brings her to his home, listens to her story, and offers comfort by suggesting that given Ueda's honest and naive nature, his feelings would not be ambiguous or merely a replacement. Hiroyasu Ueda, who has followed after her, arrives and finally resolves the misunderstanding. He explains to Yumi that just as he loved his wife because she was her own person named Yumi, he cherishes the human Yumi precisely for who she is, not as a copy. This reconciliation allows them to resume their relationship, as Yumi finally understands that she is valued for herself.

Within the larger narrative, Yumi serves as a parallel and a contrast to other characters exploring love and technology. Her crisis directly confronts the series' central question of whether genuine love can exist between humans and persocoms versus humans and other humans. While the main plot follows Hideki's developing feelings for Chii, Yumi's arc demonstrates that human relationships are also fraught with the pain of abandonment, the fear of being replaced, and the challenge of accepting a partner's past. As a character, Yumi is a key figure in the supporting cast, acting as a confidante and a point of relatability for Hideki as he grapples with his own emotions. Her primary development involves moving from a state of jealous insecurity and a belief in the superiority of machines to accepting her own worth as a unique individual capable of being loved on her own terms. Apart from her emotional resilience, she does not possess any notable superhuman abilities; her strength lies in her capacity to confront her own painful feelings and ultimately choose happiness.