Karin Kikuhara, a 15-year-old candidate pilot at Shimoji airbase, presents as quiet and frequently distracted, often absorbed in texting rather than her surroundings. This detachment is rooted in childhood trauma after her parents' deaths left her without family, starkly evident during an airbase festival where friends must intervene. Despite her aloof demeanor, she demonstrates exceptional technical skill as a navigator, executing rapid, complex course corrections with machine-like precision during missions. A defining trait is her intense fear of cats, particularly the base cat Alice, though the phobia's origin remains unclear. Karin also exhibits a notably large appetite, consuming substantial food without weight gain. Initially a comedic trait, this "Big Eater" tendency connects to a significant plot development: collapsing during a mission leads to her capture by government agents and the revelation she harbors an asymptomatic alien virus from the comets threatening Earth. This infection suppresses emotions, rationalizing her earlier detachment. The virus creates internal conflict, especially regarding its propagation through kissing. In a critical moment, Karin consciously prevents herself from kissing Mikaze Honjou to avoid spreading the infection, demonstrating her willpower against the virus's influence. Over time, she learns to coexist with it, regaining emotional expression while retaining her appetite, which shifts back toward comedic elements. Her relationships with fellow pilots Mikaze, Shizuha, and Ayamo anchor her emotionally, providing support during isolation and enabling collaboration on critical missions like comet interception. Her backstory includes implied connections to Tsukino, who reportedly knew her during childhood on a space station, though these connections lack full resolution.