Nazuna Takanashi is the youngest sibling in the Takanashi family, an 11-year-old elementary school student who turns 12. She possesses brown hair and brown eyes. Her height increases from 1.70 meters in Season 1 to 1.74 meters by Season 3, nearly matching her older brother Souta Takanashi's height—a development causing him significant distress. As the fourth sister among five siblings, her older sisters are Kazue, Izumi, and Kozue, with Souta being her only brother. Her father is deceased, and her mother, Shizuka Takanashi, is largely absent due to work. Outwardly mature and responsible for her age, Nazuna also displays mischievous behavior. She feels deep affection and protectiveness towards Souta, stemming from childhood observations of his mistreatment by their older sisters. This motivates her declared goal to become the "elder killer" to defend him, though only Izumi remains un-targeted by her rebellious intentions. Despite her loving demeanor, she exhibits manipulative tendencies, using her perceived innocence to influence her sisters—a trait unsettling Souta, who fears she may develop sadistic traits like their older siblings. Her relationship with Souta is central. She assists him with household chores, offers advice on managing their sisters, and openly respects him, contrasting with the other sisters' behavior. However, she misunderstands key aspects of his life, notably believing he is a masochist and mistakenly identifying Mahiru Inami as his girlfriend. This misconception led her to seek Kozue's guidance in learning violent behavior to "please" Souta. Her growth spurt exacerbates Souta's anxieties, symbolizing her progression toward adolescence and potential alignment with her sisters' domineering traits. Nazuna occasionally works as an unpaid intern waitress at Wagnaria restaurant, leveraging a school report assignment as justification and bribing the manager to secure the position. Her elementary school status limits her stamina, preventing late-night shifts. This intermittent involvement provides insight into the restaurant's dynamics but remains secondary to her familial role.