In the August edition of Square Enix’s Monthly Shonen Gangan magazine, the final chapter of Nachiyo Murayama’s manga adaptation, “The Mercenary and the Novelist” (Yōhei to Shōsetsuka), was published. This manga is based on Asovu Minami’s light novel series of the same name. The third and concluding volume of the manga will be released in September.

The manga made its debut in September 2021 within the pages of Monthly Shonen Gangan, featuring original character designs by TAKOLEGS. Square Enix released the first compiled volume of the manga in March 2022, followed by the second volume in September 2022.
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Manga UP! Global handles the English publication of the manga and provides the following description for the story:

In a world where the transcontinental railroad has ushered in an era of steam locomotives, the cities are shrouded in smoke, and mercenaries have become obsolete. Sword, a down-on-his-luck mercenary, reluctantly accepts a job from the renowned novelist, Verderon. Together, they embark on a perilous journey to an uncharted and treacherous mountain… only to find themselves entangled in a conspiracy involving the church and the state!
Prepare for a captivating narrative that combines iron swords and typewriters!
Minami initially published the original novel series on the Shōsetsuka ni Narō (Let’s Become Novelists) website in May 2014. The first volume of the novel, featuring illustrations by TAKOLEGS, was released by Star Seas Company in July 2019. The second volume, which includes the novel’s second part titled “Yōhei to Shōsetsuka 2: The Doll Across the Horizon,” was published in April 2021.
Source | Monthly Shonen Gangan August issue