Natsuko Tokiwa is a 20-year-old Japanese Level 5 Clairvoyant affiliated with the organization B.A.B.E.L., where she works as a receptionist and serves on the esper team The Double Face. Her clairvoyance manifests as perceiving objects, people, or locations without direct sensory contact within a defined operational range. She possesses aubergine hair and petrol-colored eyes.

Natsuko partners with Hotaru Nowaki in B.A.B.E.L.-related activities and missions, a collaboration featured in the supplemental OVA *Generous Treatment! Natsuko and Hotaru's B.A.B.E.L. Report*. Her given name, Natsuko, combines characters signifying "apple tree," "haven/port," and "child," while her surname, Tokiwa, means "always, ever" and "board/record." This naming references the "Tokonatsu" chapter from *The Tale of Genji*.