Kōji Natsumi is a Japanese novelist recognized as the original creator of the light novel series Girly Air Force. In this capacity, Natsumi is the author of the source material that spawned a manga adaptation and an anime television series. The light novel series began publication on September 10, 2014, under ASCII Media Works' Dengeki Bunko imprint, with illustrations provided by Asagi Tōsaka. As of June 2019, twelve volumes of the light novel had been released. The narrative of Girly Air Force is a military science fiction story set in a world where humanity is under attack by a mysterious force known as the Xi. To combat this threat, mankind develops advanced fighter units called Daughters, which are operated by cyborg girls known as Anima. The plot follows a young man named Kei Narutani who becomes emotionally bonded with an Anima named Gripen and joins the project to aid in the fight.

The success of Natsumi's original light novel led to its adaptation into other media. A manga adaptation illustrated by Takahiro Seguchi was serialized in Kadokawa Shoten's Monthly Shōnen Ace magazine from October 26, 2018, to May 26, 2019, and was compiled into two volumes. Furthermore, a twelve-episode anime television series adaptation was produced by the studio Satelight, directed by Katsumi Ono, and aired from January 10 to March 28, 2019. These adaptations confirm Kōji Natsumi's role as the foundational creator whose work provided the story and world for a broader multimedia franchise.