Kazumasa Hayami is a Japanese author and the original creator behind several works that have been adapted into films, television dramas, and anime. Born in 1977 in Kanagawa Prefecture, he made his literary debut in 2008 with the novel "Hyakuhachi" (108), which became a bestseller and was subsequently adapted into a film and a manga.

Hayami is credited as the original creator of the anime "Kanashiki Debu Neko-chan" (The Sad and Fat Cat). This work began as a serialized illustrated story written by Hayami with illustrations by Karin Kanō, published in the Ehime Shimbun newspaper from April 2018 to November 2018. The story was later compiled into a single volume by Shueisha in March 2019, and a television anime adaptation produced by Cyclone Graphics inc. premiered on NHK General in December 2021.

Beyond this anime, several of Hayami's other literary works have been adapted for the screen. His novel "Betsuri made 7-nichi" (7 Days Until Goodbye) was adapted into a film in 2014, and his award-winning mystery novel "Muzai no Tsumi" (Innocent Sin) was produced as a television drama. "Muzai no Tsumi" won the 68th Japan Mystery Writers Association Award in the novel and short story collection category in 2015. His other notable works include the novel "Shousetsu-ou" (The Novel King) and the bookstore-nominated "Tenchou ga Baka Sugite" (The Manager is Too Stupid). His body of work demonstrates a recurring pattern of critical and commercial success that frequently leads to adaptations across different media, establishing his significance in contemporary Japanese publishing and entertainment.