Izumi Takanashi, the 28-year-old second eldest of the Takanashi siblings, works as a romance novelist. She writes exclusively with fountain pens, resulting in ink stains daubing her face and clothing. This occupation contributes to her perpetually disheveled appearance: messy hair, no makeup, and a consistent preference for black clothing. Her reclusive habits, rarely leaving her room, foster a sickly demeanor and frail health. This physical weakness prevents her from performing household chores or lifting anything heavier than a pen without suffering muscle aches lasting several days. Consequently, she depends heavily on daily care from her younger brother, Souta Takanashi, and relies on taxis for necessary travel. Personality-wise, Izumi frequently despairs over writer's block and looming deadlines, intensifying her reclusive tendencies. She harbors deep anxiety that Souta might neglect her should he enter a romantic relationship, reflecting her profound dependence on him. Despite self-absorbed habits, she demonstrates protective instincts toward Souta, having shielded him from their sisters' mistreatment in childhood. Occasional naivete surfaces, such as mistakenly assuming Souta was a pedophile upon learning of his interest in a female coworker. Family dynamics significantly shape her character. Her mother, Shizuka Takanashi, is largely absent due to work but occasionally makes demanding requests, like compelling Izumi to cook despite her protests about physical strain. Izumi resembles a younger Shizuka and proves a competent cook when forced into the task. Her siblings are Kazue (eldest sister), Kozue (third sister), Nazuna (youngest sister), and Souta (only brother). She shares an especially close, though dependent, bond with Souta, who manages most domestic responsibilities for her and Kozue in their mother's absence. A key development occurs when Izumi enters severe writer's block upon suspecting Souta is dating his coworker Popura Taneshima, fearing it would end his care for her. During this slump, she impulsively leaves home and encounters Mahiru Inami, another Wagnaria employee, who helps alleviate her distress. Souta then tends to her recovery, underscoring their interdependence. In the spin-off *A Time in the Universe*, she becomes a primary protagonist, joining Dylan Andrews and Jax Jones on a mission after Dylan's initial reluctance; Souta negotiates her inclusion by promising to oversee her well-being. Her name holds etymological significance: "Izumi" means "fountain" or "spring," referencing her writing tools, while "Takanashi" combines "little bird" (小鳥) and "play" (遊). She shares a familial naming pattern with her sisters, all featuring "zu" as their second character—unlike Souta, whose name breaks this convention.