Bungou Stray Dogs Gaiden: Ayatsuji Yukito VS. Kyougoku Natsuhiko tells the story of the "homicide detective" Ayatsuji Yukito and his assistant Mizuki Tsujimura as they try and solve a mysterious murder case at the request of the government. Their search eventually leads them to Yukito's old nemesis and public enemy Kyougoku Natsuhiko.