Kumi Kawamura is a sixth-grade student at Elementary School No. 9 and a core member of the school's Alien Party, a group tasked with capturing extraterrestrial creatures that appear on campus. She is recognized as the most independent and capable member of the team, having long served on the Student Council and shouldered a heavy share of responsibilities both at school and at home. Her father passed away when she was four years old, leaving her to assist her widowed mother with writing work and an above-average number of household chores. This early burden fostered a mature, dutiful, and self-reliant disposition, though it also contributed to an outwardly cool and emotionally reserved demeanor, shaped by years of being relied upon by her classmates and teachers. Kumi possesses a sharp, well-read mind and a practical outlook; she approaches alien encounters with calm resolve where others might panic, displaying a rational and strategic mindset far beyond her age.

Within the story, Kumi initially joins the Alien Party with little enthusiasm, viewing it as yet another obligation to be met with composure. As events unfold, her natural leadership instincts and protective instincts toward her teammates—particularly the anxious Yuri Otani and the seemingly perfect Kasumi Tomine—become central. Her bond with Kasumi is complicated by the traumatic Yellow Knife incident, in which Kasumi's fusion with the alien leaves her unstable. Kumi's wariness of Kasumi's changed behavior drives her to investigate alone, leading to a fatal attack in the school library. In the manga continuity, she is killed by a Lynax alien and subsequently revived through an emergency reconstruction that merges her with her Borg symbiont, transforming her into a permanent hybrid between human and alien protector. This fusion not only saves her life but grants her enduring Borg abilities, eliminating the need for an externally attached Borg. Her return unsettles her friends and adds a layer of existential unease, yet she remains committed to safeguarding them from further threats.

Kumi's abilities revolve around her partnership with a Borg, a sentient, shape-shifting organism that bonds with its host to provide weaponry, defensive adaptations, and sensory enhancements during alien combat. Her Borg manifests in a light purple hue and can generate rollerblades for mobility, tranquilizing projectiles, and other tools suited to capturing aliens. After her fusion, she essentially becomes a living Borg, retaining those combat capabilities in a more integrated form. Despite her formidable skills, her true strength lies in her composure under pressure and her unwavering sense of responsibility, which guides her actions even when confronted with the series' escalating horrors and the blurred boundaries between human and alien existence.