Ryō Hiromatsu is the Japanese author and original creator of the web novel, light novel, and manga series Uglymug, Epicfighter, known in Japanese as Busamen Gachi Fighter. Hiromatsu first launched the story as a web novel on the user-generated novel publishing website Shōsetsuka ni Narō, where it was serialized online from February 2015 to October 2022. The central premise follows Shigeru Yoshioka, a former salesman whose life collapses after he is falsely accused of a crime, leading him to withdraw from society. He discovers a way to travel to another world through his computer, where a status screen offers him a choice: sacrifice his looks in exchange for immense power. Accepting this deal, he is reborn in a fantasy world with an ugly appearance but overwhelmingly high combat abilities, effectively becoming an absolute god in terms of strength, though he must contend with weaknesses such as experiencing pain when touched by women.

The success of the web novel led to several official adaptations. A light novel version, illustrated by Akira Banpai, was published under Kobunsha's Kobunsha Light Books imprint on May 18, 2018. A manga adaptation, illustrated by Osamu Kozuki, was serialized in Square Enix's seinen manga magazine Monthly Big Gangan from November 2017 to December 2020, and was collected into six tankōbon volumes. The manga is published in English by Square Enix on its Manga Up! Global app. A sequel manga, Busamen Gachi Fighter SSS, also illustrated by Kozuki, was serialized from December 2024 to September 2025 and collected into two volumes.

An anime television series adaptation of Uglymug, Epicfighter was produced by Egg Firm and animated by White Fox. The series was directed by Toshiyuki Sone, with Kenta Ihara handling series composition and Junichi Suwabe voicing the protagonist Shigeru Yoshioka. It aired on Tokyo MX and other networks from July to September 2025, running for twelve episodes. Hiromatsu is credited as the original creator of the work upon which all these adaptations are based. The story blends isekai and fantasy genres with a comedic yet earnest exploration of its protagonist's journey, focusing on themes of social isolation, superficial judgments based on appearance, and the search for meaningful companionship despite self-imposed weaknesses.