Natsuki Taga attends high school alongside Shō Fukamachi and Tetsurō Segawa. An enthusiastic Sci-Fi Club member, she maintains a semi-close friendship with Tetsurō, often ensuring he submits his schoolwork on time. Her relationship with Shō appears distant or non-existent. Initially presented as a minor side character involved in typical school activities and club life, her narrative role adds background depth with no foreshadowing of her later significance or the depth of her dedication.

Following the Chronos Corporation's global takeover (X-Day), Natsuki becomes the essential caretaker for the Mt. Minakami survivors: Tetsurō Segawa, Mizuki Segawa, Yohei, and Shizu. In this critical role, she provides vital support and stability, revealing unexpected resilience and demonstrating strong responsibility and compassion. Her Christian faith is explicitly noted during this period, though its specific influence remains undetailed. This caretaker role, emphasizing her loyalty and resourcefulness in dire circumstances, becomes a consistent aspect of her character across media.

Within expanded narratives like the *Son of Mine* universe, Natsuki continues caring for the Mt. Minakami group. She exhibits concern for Shizu's well-being and shows distinct curiosity upon encountering Aptom, a Chronos "Lost Number" commando with shape-shifting abilities. This interaction suggests an openness to unconventional individuals, though her involvement remains supportive, not combative. Her development centers on unwavering commitment to protecting and sustaining the group amid ongoing threats, without significant physical or power-based evolution. Across all official portrayals, she functions as a grounding force for other characters, devoid of direct battle participation or supernatural elements.