Miyabi Koto, daughter of Professor Koto, approaches archaeologist Koichiro Kamishiro after her father's death, seeking to assist him. Her motivation stems from continuing her father's research. This collaboration triggers Kamishiro's intensified investigation into the Crystal Triangle and the "Message of God."

During an Mt. Aso expedition, Miyabi undergoes supernatural transformation when Himiko—an ancient Yamatai high priestess—possesses her after the destruction of Himiko's shrine. Through this possession, she reveals critical details about the Sacred Mirror Yatanokagami: it was stolen a millennium earlier by monk Kukai and serves to prevent mankind's annihilation.

Miyabi actively joins Kamishiro's subsequent missions across Japan, including searches for Kukai's Temple in Kyoto and expeditions to Hokkaido. These endeavors involve evading pursuit by the CIA, KGB, and Japanese Ministry of Intelligence, alongside confrontations with the extinction-seeking alien Hih Tribe. Her involvement remains essential to uncovering the divine message's final components tied to Earth's survival.

Her relationship with Kamishiro develops into mutual romantic interest, adding emotional weight to their quest. This dynamic reinforces her role as both a key participant in the archaeological and spiritual conflict and a personal anchor for Kamishiro amidst escalating threats.