Natsuki Taga is a high school student and a friend of Tetsuro Segawa. She is a member of the school's science fiction club, where she shows an enthusiastic and dependable nature, often taking responsibility for ensuring that club duties and assignments are completed on time. She has black hair and black eyes.

In the story, Natsuki initially appears as a background character within Tetsuro's social circle. After the events known as X-Day, when the scope of the Chronos Corporation's threat becomes clear, she steps up to help Tetsuro, Mizuki Segawa, and Shō Fukamachi. She decides to join their cause once she learns the full extent of Chronos's criminal activities and the danger they pose to humanity. Her main contribution comes through her skill in gathering information, which she uses to support the group in their struggle against the organization.

Natsuki's development is marked by her transition from an ordinary schoolgirl with casual interests to a committed ally willing to face a global conspiracy. She does not possess any superhuman abilities or combat training; instead, her value lies in her resourcefulness and loyalty. Her key relationships are with Tetsuro, as a school friend, and with the wider group of protagonists who resist Chronos. She appears in the later episodes of the original video animation, specifically in episodes four and five, where she begins to take an active supporting role.