The rumors about Ikebukuro spread like wildfire, especially those regarding the dangerous color gangs and the infamous legend surrounding the Black Rider. Miyoshi Yoshimune transfers to Raira Academy due to his parents' work and quickly befriends Mikado Ryuugamine, Masaomi Kida, and Anri Sonohara—who all soon advise him to stay away from the gang members and not believe nonsensical myths for his own protection.

However, no one is safe once they cross paths with Izaya Orihara, Shinjuku's notorious information broker. The three friends insist that Izaya is merely making jokes, but when Yoshimune runs into Izaya by himself, Izaya gives him a task: to look into the unknown people who are currently investigating the color gangs and relay the information back to him. Although Yoshimune tries to avoid Ikebukuro's underworld, Izaya's request leads him to a fateful encounter with a girl named Chiaki Igarashi, marking only the first step into uncovering Ikebukuro's biggest scheme yet.