月刊少年エース
A manga based on the light novel "Beast", which is illustrated by Shiwasu Hoshikawa, debuted on December 26, 2019 in the February 2020 issue of "Monthly Shōnen Ace". This spin-off manga features Ryūnosuke Akutagawa, who joins the Armed Detective Agency, and Atsushi Nakajima as a subordinate of the Port Mafia.