Set in an alternative world of Bungo Stray Dogs, this "what-if" story imagines if Atsushi Nakajima was in the Port Mafia and Ryūnosuke Akutagawa was in the Armed Detective Agency, instead of vice-versa. The story follows Ryūnosuke Akutagawa, who vows revenge on a man dressed in black in order to rescue his sister. However, as he is about to starve to death, a man from the Armed Detective Agency appears.

Bungo Stray Dogs the Movie: BEAST

Kengo, who is saddened by the loss of his girlfriend Sayuri in an accident, meets an eccentric high school girl, Umihana. Her father, Shaman Tetsushi, makes Kengo see Sayuri's spirit and begins living with Sayuri again.  Sayuri is cute. It's a ghost, but I'm not scared at all.  On the contrary, he enthusiastically teaches the recipe to Kengo, who cannot cook, until he can reproduce the same taste as Sayuri.  Even though I can see the dream of music and the spirit of my lover so clearly, I can't grasp it.  Even though he had such itchy days, he was still happy.  However, one day, a so-called love triangle incident occurred in which the prayer's daughter, Kaika, liked Kengo.  Umihana had a bad taste of exorcising anything, whether it was a demon or a kind-hearted spirit.