In Tokyo's downtown district of Ikebukuro, amidst many strange rumors and warnings of anonymous gangs and dangerous occupants, one urban legend stands out above the rest—the existence of a headless "Black Rider" who is said to be seen driving a jet-black motorcycle through the city streets.
Mikado Ryuugamine has always longed for the excitement of the city life, and an invitation from a childhood friend convinces him to move to Tokyo. Witnessing the Black Rider on his first day in the city, his wishes already seem to have been granted. But as supernatural events begin to occur, ordinary citizens like himself, along with Ikebukuro's most colorful inhabitants, are mixed up in the commotion breaking out in their city.
A bonus episode taking place between the two halves. Glowing discs are spotted throughout Ikebukuro. Meanwhile, confusion erupts when multiple criminal groups lose track of identical bags simultaneously. Also, Anri is wearing cat ears and a Yukata, Mikado has rabbit ears, and Masaomi is a harlequin. Walker believes that reality has stolen a story he is working on.
This is Episode 12.5 of Season 1.
Yuuhei hosts a show searching for the loveliest couple in Ikebukuro, the winner of which gets to appear in one of his movies. As Mikado and Anri go to the movies together, hoping to clear everything up between them, they are interviewed by Yuuhei. A guy with a knife tries to attack Yuuhei, but he is stopped by Shizuo, who is also being hounded by Izaya's sisters wanting to meet Yuuhei. Shizuo then encounters Izaya, who arranged for the attack, and enters a huge fight with him which escalates throughout Ikebukuro, prompting Celty to move into action. As the fighting escalates, several smaller fights break out, forcing Celty to use her powers to stop everyone.
This is Episode 25 of Season 1.
One night, Mikado Ryuugamine accepts an invitation to Shinra Kishitani's apartment, eager to talk to Celty as quite some time has passed since the two last spoke. But, much to his astonishment, he finds that a large group of Ikebukuro's finest has gathered there for a hot pot party.
Already confused with the current situation, Mikado is further surprised to see that his friend and fellow Raira Academy student Anri Sonohara is there as well. As the two decide to take a seat together, a few members of the group begin reminiscing over events from days past: Mikado recalls an adventure from his childhood with Masaomi Kida, Anri explains how she came to be friends with Mika Harima, and Shizuo Heiwajima tells of his first meeting with Tom Tanaka.
This is Episode 4.5 of Season 2 (Durarara!!x2 Shou).
In spite of the mayhem that has been taking place in Ikebukuro, Shinra Kishitani and Celty Sturluson have decided to go on a short trip. Excited to finally be going out with the one he loves, the underground doctor makes it his priority to give Celty his undivided attention, even if it means rejecting phone calls from his good friend Izaya Orihara.
However, despite his hopes of having a peaceful holiday, Ikebukuro's various residents continue trying to reach him. Furthermore, just as Shinra begins to enjoy reminiscing about old memories on a carriage ride together with his beloved, Celty starts to notice a strange presence...
This is Episode 13.5 of Season 2 (Durarara!!x2 Ten).
The episode revolves around the man with "the worst luck in Ikebukuro," Shizuo Heiwajima, and another blonde-haired, sunglasses-wearing man wearing a bartender outfit named Shidzuo Nobusuma. Shidzuo is a young hoodlum. As the two men's fates are entangled, a new legend is born on the streets of Ikebukuro.
This is Episode 19.5 of Season 2 (Durarara!!x2 Ketsu).