Ishio Yamagata is a Japanese light novel author and manga writer known for creating fantasy series that often blend action with complex, mystery-driven narratives. Born in 1982 in Kanagawa Prefecture, he studied literature at Tokai University before beginning his professional writing career.

Yamagata debuted as a writer while still a university student, winning the grand prize in the fourth Super Dash Bunko Novel Rookie Award. His winning entry was the first volume of what would become his initial series, Tatakau Shisho to Koisuru Bakudan (The Fighting Librarian and the Love Bomb). This work laid the foundation for the larger Tatakau Shisho franchise.

The Tatakau Shisho series, also known as The Book of Bantorra, began with the publication of its first light novel volume on September 22, 2005, under Shueisha Super Dash Bunko imprint. The original light novel series, illustrated by Shigeki Maeshima, concluded on January 22, 2010, after ten volumes. The story is set in a world where the deceased transform into stone-like books stored in the Bantorra Library, following the Armed Librarians who protect these books and battle the Shindeki Church cult. A manga adaptation titled Tatakau Shisho to Koisuru Bakudan, illustrated by Kokonotsu Shinohara, was serialized in Shueisha online magazine Ultra Jump Egg from March 2008 to October 2009, eventually compiled into three volumes. An anime television series adaptation, The Book of Bantorra, was produced by studio David Production and aired 27 episodes from October 2009 to April 2010.

Following the conclusion of Tatakau Shisho, Yamagata launched his next major series, Rokka: Braves of the Six Flowers (Rokka no Yūsha). The light novel series, illustrated by Miyagi, began publication on August 25, 2011, also under Shueisha Super Dash Bunko imprint. Six main volumes have been released, with the most recent appearing in July 2015. A manga adaptation illustrated by Kei Toru began serialization in February 2012 and was collected into four volumes. An anime television series produced by studio Passione aired 12 episodes from July to September 2015. Both the light novels and manga have been licensed for English publication in North America by Yen Press. The story follows six heroes chosen by the Goddess of Fate to defeat the Demon God, but when seven individuals gather at the appointed meeting place, they realize one among them is an impostor, leading to a locked-room mystery within a fantasy setting.

Yamagata is credited as the writer for both the light novel and manga versions of Rokka: Braves of the Six Flowers. His creative identity is characterized by dense, meticulously constructed narratives with interconnected story elements that become apparent through repeated reading. His works often feature ensemble casts rather than a single protagonist, as seen in The Book of Bantorra, and incorporate mystery elements alongside fantasy adventure.