Fuse is the original creator of the massively popular multimedia franchise That Time I Got Reincarnated as a Slime, known in Japan as Tensei Shitara Slime Datta Ken. Fuse is a pseudonymous author who first began the series in 2013 as a web novel on the user-generated content site Shōsetsuka ni Narō, where it was serialized until 2016. At the time, Fuse was working as a salaryman in Osaka Prefecture, writing the story primarily for practice and personal enjoyment before eventually submitting it to publishing competitions. This initial serialization formed the foundation for what would become a major commercial success.

The series was acquired for print publication by Micro Magazine, which released the first light novel volume, illustrated by Mitz Vah, in May 2014 under its GC Novels imprint. The light novel series has since been published in multiple volumes, with the English language release handled by Yen Press. A manga adaptation of the main story, illustrated by Taiki Kawakami, began serialization in Kodansha's Monthly Shōnen Sirius in March 2015, and it is this manga version that served as the primary source material for the subsequent anime adaptations.

Beyond the main storyline, Fuse has been credited as the original creator for numerous spin-off manga series that expand the franchise's world. These include The Slime Diaries: That Time I Got Reincarnated as a Slime, illustrated by Shiba, which depicts the comedic daily life of the characters; That Time I Got Reincarnated as a Slime: The Ways of the Monster Nation, illustrated by Shō Okagiri; and That Time I Got Reincarnated (Again!) as a Workaholic Slime, a gag comic illustrated by Shizuku Akechi that reimagines the protagonist in a corporate setting. A later spin-off novel series, Toaru Kyūka no Sugoshi-kata, was serialized on Shōsetsuka ni Narō beginning in 2023.

The anime adaptations of the franchise, produced by studio Eight Bit, have also been closely tied to Fuse's original work. The first season of the anime premiered in October 2018, with subsequent seasons and films following. For the 2022 film That Time I Got Reincarnated as a Slime: Scarlet Bonds, Fuse personally wrote the original story, marking a direct contribution to the animated side of the franchise. Fuse has also been involved in the creative process for the manga adaptations, providing input on plot adjustments and structure, as well as writing short stories to accompany the serialized releases.

Regarding Fuse's artistic identity, the creator has maintained a private public persona, with no official social media accounts or public appearances. In interviews, Fuse has stated that the initial writing of the series was done without a long-term plan, and the nation-building theme that defines the story was only recognized during the editing process for the second light novel volume. The choice of a slime as the protagonist stemmed from the idea of using the most familiar monster in fantasy settings to explore the isekai genre from an unconventional perspective.

The industry significance of Fuse's creation is substantial, with the franchise achieving worldwide commercial and critical success. The combined circulation of novels and manga, including spin-off works, has exceeded 45 million copies globally, while the anime adaptation has accumulated billions of views. The series has consistently ranked highly in annual light novel and manga sales charts, and it has become a defining title within the isekai genre.