A dragon of Earth, Nataku is an androgynous clone of extreme psychic ability, born of genetic material of Toujou Kazuki, the deceased granddaughter of the president of Toujou Pharmaceuticals, and her father Masaki. They are sent to retrieve the Shinken by the Chairman Toujou who wishes to destroy the sword so that Nataku cannot become entangled in the matter of the Promised Day.

In the process of stealing the Shinken, Nataku mortally wounds Kyougo — Fuuma and Kotori's father — who was attempting to protect the Shinken. Nataku is haunted by the memories of its previous life as Kazuki, and follows Fuuma unquestionably as Fuuma resembles the person Kazuki cared most for — her father.

In Tsubasa Reservoir Chronicle:

Nataku is one of the fighters of the City Hall faction. Unlike in X, he is a mentally developed adult and takes care of Kazuki, alternate version of X's Kazuki, who takes Seishirou's place.