Keiko Ōkura, nicknamed "Okei", is a 16-year-old student at Yamashiro Academy and one of three psychics. She wields telepathy for mental communication and perception, alongside teammates Yumi Sado (precognition and teleportation) and Mai Ishiki (superhuman strength when angered).

Her personality is impulsive and emotionally driven. This impulsiveness leads her to test an arcade psychic power machine, causing it to explode and attracting unwanted attention. She develops a romantic interest in Hiro Nimura, director of the Psychic Power Research Society (PPRS), readily believing his demonstrations of psychic power. Trusting Hiro, she actively seeks him out, culminating in her capture by a rival esper group during an attempt to rescue him from Rika Matoba.

Keiko experiences profound disillusionment upon Hiro's betrayal, where he supplies anti-esper suppression bracelets that neutralize their powers. Her romantic feelings for Hiro dissolve completely after his attempted lobotomy of the trio, contributing to her development into greater wariness. When approached to lead the reformed PPRS, she flees with her teammates, rejecting further involvement.

Keiko appears less mature than her teammates despite sharing their age. Her character arc concludes as the OVA's primary conflict resolves.