Tomoko Kitazawa, the youngest member of her family, sports brown hair and green eyes. Adopted by Yukie Kitazawa alongside her sister Rumi, she shares no genetic ties with the others yet demonstrates fierce devotion to preserving their unity. Tomoko actively works to prevent separation from any family member—including Yukie's partner Taketa, Rumi, and her stepfather—expressing deep concern over tensions threatening their bond. Her innocence and persistent desire to keep the family together define her character, driving her actions even after Yukie's car accident leaves them vulnerable to blackmail by Taketo Nogawa and his father.

Tomoko participates in intimate acts with Rumi during family gatherings, reflecting her embedded role within these complex dynamics. When her stepfather returns and develops troubling urges toward her due to her physical maturity, Taketo intercedes to manage the situation and maintain stability. Navigating these escalating tensions, Tomoko's role evolves, yet her commitment to protecting the family's cohesion remains unwavering. Her dedication to familial harmony persists through every escalating challenge.