Ryū Sagawa is an original creator and writer known for work within the Ultraman franchise. He is credited under several pen names, including Ryuu Sagawa (瑳川竜) and Riku Sanjou (三条陸), with his birth date recorded as October 3, 1964.

Sagawa is the original creator behind the manga Ultraman Chō Tōshi Gekiden and its related anime adaptation. The manga was written by Sagawa and illustrated by Kurihara Jinshi, with a compiled volume released on December 25, 2009. The story was adapted into an original video animation (OVA) titled Ultraman: Chō Tōshi Gekiden - Suisei Senjin Tsuifon Tōjō, released on September 25, 1996. For this OVA, Sagawa is officially credited for both the original concept and the script, working alongside director Tetsurou Amino and character designer Naoki Oohira. The plot follows a warrior known as Fighter Ultraman as he confronts a destructive force called Comet Warrior God Tsuifon approaching Earth.

In addition to this work, the creator has an extensive career as a writer and series composer under the name Riku Sanjou, contributing to various long-running anime television series from the mid-2000s through the 2020s.