Masaru Katori is a Japanese writer and manga artist known for creating the manga series Shion no Ō. This name is a pen name; the creator behind it is Naoko Hayashiba, a former professional shogi player from Fukuoka, born on January 24, 1968. Hayashiba had a remarkable career in shogi, becoming a professional at the age of twelve and winning the Women's Meijin title at fourteen. She left the professional shogi world in 1995 and subsequently began a career as a novelist and writer. The pen name Masaru Katori was used specifically for her work on the manga Shion no Ō.

As a creator, Masaru Katori is credited as the sole writer for the manga Shion no Ō, which was serialized in Kodansha's Monthly Afternoon magazine from May 2004 to June 2008. The series was illustrated by Jiro Ando and collected into eight bound volumes. The story follows a young girl named Shion Yasuoka, who becomes mute after witnessing the murder of her parents, a crime she believes is connected to the world of professional shogi. The manga blends a mystery thriller narrative with the strategic depth of shogi, a board game similar to chess.

The work was later adapted into a twenty-two episode anime television series produced by Studio Deen, which aired in Japan from October 2007 to March 2008. In addition to the anime, a Nintendo DS video game based on the series was published by Mainichi Communications in April 2008. Through Shion no Ō, Katori's artistic identity is closely tied to the world of shogi, drawing directly from her own past as a child prodigy and professional player. The series is considered notable for its authentic portrayal of the shogi world and its psychological intensity, marking a significant contribution to the sports and mystery genres in manga and anime. After a fifteen-year absence, Naoko Hayashiba returned to professional shogi in 2010.