The first season of the anime is adapted from the first three light novels and spans 24 episodes and two OVAs. It was directed by Takahiro Omori and produced by studio Brain's Base with subtitled episodes available within 24 hours on Crunchyroll. The English dub was produced by Aniplex of America at Bang Zoom! Entertainment and broadcast on Cartoon Network's Adult Swim from June 26 to December 17, 2011. It is licensed by Anime Limited in the United Kingdom and Beez Entertainment in Europe.
In Tokyo's downtown district of Ikebukuro, amidst many strange rumors and warnings of 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, soundless 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.
The second season of the anime is adapted from light novels four through thirteen and was broken up into three cours of 12 episodes and one OVA each. The second season was announced on Anime News Network on March 15, 2014, and the cours, titled Shou, Ten, and Ketsu, began airing in January 2015, July 2015, and January 2016 respectively. It was directed by Takahiro Omori and produced by studio Shuka with subtitled episodes streamed on Crunchyroll. The English dub was produced by Aniplex of America and is available on Crunchyroll, Funimation, and Hulu.
Each cour of Durarara!!x2 holds a title that follows the classic structure of Japanese storytelling, Kishōtenketsu (起承転結). Shou (承, lit. understanding): the development, Ten (転, lit. motion): the twist, and Ketsu (結): the conclusion. While season one did not hold a title, it would be Ki (起) to represent introduction.
Shou picks up six months after the end of season one. Peace has finally returned to Ikebukuro, but soon new characters appear in the city and troubles slowly begin to build, throwing the city and everyone in it right back into chaos.
Ten continues where the end of Shou left off. Mikado begins putting his plans for the Dollars into effect. Many characters' daily lives are explored and pasts revealed as their lives continue to intersect within the story.
Ketsu is the conclusion to the series and continues where Ten left off. The time has finally come that Celty has a chance of reuniting with her head, and the final battle between Izaya and Shizuo commences as the full cast comes together in the final conflict in the story.