"Durarara!!×2 Shō Gaiden!?" is a three-episode OVA series that serves as a side story to the main "Durarara!!×2" narrative. The story unfolds in Ikebukuro, a bustling district of Tokyo, where various factions, individuals, and supernatural elements intersect. The focus shifts to the Dollars, a mysterious online gang, and their interactions with other groups like the Yellow Scarves and the Blue Squares. Central to the plot is the enigmatic Izaya Orihara, an information broker who manipulates events from behind the scenes, often for his own amusement.

The narrative explores the backstory of Shizuo Heiwajima, a man with superhuman strength who works as a debt collector, and his tumultuous relationship with Izaya. Shizuo's violent tendencies and his desire to live a normal life are contrasted with Izaya's chaotic and manipulative nature. Meanwhile, Celty Sturluson, a Dullahan searching for her missing head, continues to navigate her life in Ikebukuro alongside her human partner, Shinra Kishitani. Their relationship is tested as Celty grapples with her identity and purpose.

The OVA also delves into the lives of other key characters, such as Mikado Ryuugamine, the founder of the Dollars, who struggles with his dual identity and the consequences of his actions. Anri Sonohara, a quiet girl harboring a dangerous secret, becomes entangled in the conflicts between the gangs. The series further explores the dynamics of the Dollars, revealing how its members, both ordinary and extraordinary, are connected through their shared experiences in Ikebukuro.

Themes of identity, loyalty, and the consequences of one's actions are woven throughout the narrative. The OVA provides additional context to the main series, offering deeper insights into the motivations and relationships of its characters. The interconnected lives of Ikebukuro's residents, combined with the district's chaotic energy, create a compelling backdrop for the unfolding drama. The series maintains the intricate storytelling and character-driven focus that defines the "Durarara!!" franchise, while expanding on the world and its inhabitants.