Hina Takanashi is the youngest of the three Takanashi sisters, initially a three-year-old daycare attendee. As the biological daughter of Yuri Takanashi, she is the only sister directly blood-related to their uncle and guardian, Yuuta Segawa. This connection significantly shapes family dynamics and fuels Yuuta's determination to keep the sisters together after their parents vanish.

Exceptionally cheerful, friendly, and trusting, Hina shows little fear of strangers. Her speech features frequent mispronunciations, often omitting consonants; she calls Yuuta "Oi-tan" instead of "Oji-san" due to difficulty with the "j" and "s" sounds. She adores the fictional heroine anime "Luna Luna Seven," which influences her interests. A distinctive trait is her attachment to a stuffed bunny plushie, a gift from her mother Yuri, carried regularly as a comfort object.

Her development centers on gradually understanding her parents' absence. Following the plane crash leaving Yuri and her husband missing and presumed dead, Yuuta, Sora, and Miu carefully shield Hina, preserving her emotional well-being with the explanation of an extended trip. This protective approach holds until Sora eventually breaks the news. Despite initial sadness, Hina resolves to keep smiling for her family's sake.

Her presence acts as a unifying force, charming neighbors, acquaintances, and even initially strict figures like the landlady, leading to increased support for Yuuta's guardianship. Her spontaneous friendship with a neighbor’s elderly mother indirectly helps resolve an eviction threat.

In OVA episodes set years later, Hina is an eight-year-old second-grade elementary student. Her speech becomes clearer, yet she retains core optimism and affection. She continues carrying her bunny plushie, symbolizing her enduring connection to her past while adapting to her family reality. Her journey reflects a transition from early childhood innocence to a more aware yet hopeful perspective, consistently acting as an emotional anchor for the family.