Kiichi Kosuzu is a Japanese light novel author and the original creator behind the multimedia franchise The Reincarnation of the Strongest Exorcist in Another World. Writing under the name Kiichi Kosuzu, the creator began the story as a web novel on the user-generated platform Shōsetsuka ni Narō in December 2018. The series garnered enough attention to win the 7th Net Novel Award, leading to its acquisition by publisher Futabasha. The light novel was first published in print on July 31, 2019, under Futabasha's M Novels imprint. The original work is also known by its Japanese title, Saikyō Onmyōji no Isekai Tenseiki.

As the author of this series, Kosuzu has overseen its expansion into multiple media formats. A manga adaptation illustrated by Toshinori Okazaki began serialization in Futabasha's Gaugau Monster online magazine in May 2020. An anime television series adaptation produced by Studio Blanc later aired from January to April 2023, with Crunchyroll streaming the series internationally. The story follows a powerful onmyōji (exorcist) who, after being betrayed and left for dead in his original world, uses a reincarnation spell to be reborn in a new fantasy world where he applies his spiritual arts to overcome various challenges.

In addition to this flagship series, Kosuzu is also credited as the author of another light novel titled About Four People with Negative Skills Gathering and Forming the Strongest Team, published under the SQEX Novel label. The creator maintains an online presence on the Kakuyomu novel publishing website and has shared thoughts on the adaptation of the work into an anime, expressing amazement and excitement about the production. Through the success of this property, Kiichi Kosuzu stands as an example of a web novelist who successfully transitioned to traditional publishing and multimedia licensing, a common career path within the contemporary Japanese light novel industry.