Akutagawa and Atsushi devote everything they've got to an explosive final confrontation. After a desperate battle for the things most important to them, they both learn the real truth of this world. The thrilling spin-off of Bungo Stray Dogs comes to a grand conclusion!

In exchange for their assistance in tracking down his sister, Akutagawa must fulfill a condition set by each detective agency member. For his first trial, agency member Kenji Miyazawa proposes they compete in...rice planting!?

After learning that his long-lost sister, Gin, is in the Port Mafia headquarters, Akutagawa breaks free from his Agency colleagues and goes in alone-right through the front door! After four and a half years, it seems the two will finally be reunited, but...

In the parallel universe of Bungo Stray Dogs: Beast, Ryuunosuke Akutagawa’s desperate mission to save his younger sister leads to him being recruited by the armed detective agency! But standing in his way is none other than the fearsome White Reaper of the Port Mafia-Atsushi Nakajima. As darkness and light face off, what fate awaits the two...?