Tokiko Tachibana, later Tsukiko Fujii after remarriage, is mother to Hina and Rui Tachibana, born under the maiden name Tsukiko Tachibana. Her first marriage collapsed due to Jou Mikimoto's infidelity, triggering a bitter divorce that ingrained deep distrust of men—a resentment she vocalized to her daughters, notably affecting Rui's upbringing.

Emerging from this turmoil, she formed a relationship with widower Akihito Fujii, father of Natsuo Fujii. His steadfast sincerity and commitment to support her gradually eroded her bitterness and depression, restoring emotional stability and joy. Their marriage merged both families, establishing her as stepmother to Natsuo and Akihito as stepfather to Hina and Rui.

As a stepmother, she embodies warmth, kindness, and selflessness, prioritizing others' welfare. She once contemplated divorcing Akihito, mistakenly believing their union strained their children. She extends equal affection to Natsuo despite lacking biological ties.

Physically, she possesses chest-length light brown-blond hair, typically swept with bangs falling leftward. Small wrinkles frame her usually cheerful demeanor, though mention of her ex-husband sparks visible rage.

Her name carries symbolism: "Tsukiko" merges "moon" (月, *tsuki*) and "child" (子, *ko*). Her maiden surname "Tachibana" means "orange/tangerine" (橘), while "Fujii"—adopted after marriage—combines "wisteria" (藤, *fuji*) and "well" (井, *i*).