Nagisa Hanamiya is a third-year student at Uchihama Academy and a member of the Astronomy Club, where she serves as a senior member. She also operates her own personal fan club, known as the Hanamiya Society. Nagisa comes from a highly influential and powerful family, which contributes to an air of mystery that surrounds her. She is a gifted individual, often described as a genius, but she tends to be a lonely type, keeping others at a distance despite her social standing. Her demeanor is typically calm and elegant, and she prefers to observe arguments or conflicts rather than actively intervene. This reserved nature belies a playful streak, as she enjoys teasing and bullying her fellow club member Sou Akiyama simply for her own amusement.

Within the story, Nagisa plays a pivotal role in the unfolding supernatural events. When an unnatural earthquake shakes the Astronomy Club room, she remains behind while the others investigate, and during this moment she notices a strange relic-like cube she had been toying with begins to emit a blue light. This cube later becomes a key object in the series’ central mystery, which involves the appearance of a mysterious transfer student, Yui Furukawa, and the exploration of lost futures. Nagisa’s intelligence and composed nature make her a steady presence among her friends, even as strange occurrences escalate. Her family history also ties into the plot: her great-grandmother was a renowned scientist who researched and developed technology at a nearby military manufacturing plant, and the Hanamiya family villa later serves as a setting for the group’s summer vacation, where deeper connections to the lost future are uncovered.

Nagisa’s key relationships are mainly with her Astronomy Club peers: Sou Akiyama, the male lead whom she enjoys teasing; Kaori Sasaki, the childhood friend; Airi Hasekura; and Kenny Osafune. She is also instrumental in helping Yui Furukawa integrate into the school after Yui’s sudden appearance. Throughout the series, Nagisa’s mysterious aura and hidden depths are slowly revealed, though she remains an enigmatic figure whose true motivations and past are only partially explored. Her notable abilities are not explicitly combat-oriented; instead, she demonstrates sharp intellect, observational skills, and a knack for handling delicate situations with poise. Her calmness under pressure and her willingness to stay behind and observe make her an essential, if somewhat aloof, anchor in the group’s journey to uncover the truth behind the time-altering phenomena.