Natsuki Taga attends high school with Sho Fukamachi, Tetsuro Segawa, and Mizuki Segawa. She actively participates in the Sci-Fi Club, led by Tetsuro, often ensuring he completes his work on time. While her friendship with Tetsuro is semi-close, she starts off less familiar with Sho. Following Chronos Corporation's global takeover ("X-Day"), Natsuki becomes the caretaker for the Mt. Minakami incident survivors: Tetsuro Segawa, Mizuki Segawa, Yohei Onuma, and Shizu Onuma. She voluntarily oversees their well-being while they remain in hiding, a role where her Christian faith is noted.