Durarara!!x3 is the third light novel in the series. It contains the third story arc of the series, the Yellow Scarves Arc, and was adapted into volumes 8-10 of the Durarara!! manga and episodes 18-24 of the anime, closing the first season.
Ikebukuro still reels from the recent slashing attacks. A group of punks wearing yellow scarves prepare to start a gang war while a man within plans a takeover. A trio of high schoolers are said to be the tightest-knit group in school. A gang leader is trying to escape the past. The urban legend, the Black Rider, is said to be a member of the colorless gang, the Dollars. A smaller group within the Dollars ready themselves for a fight. An intel broker is looking to start a war. A couple of underground doctors are more knowledgeable and influential than they appear. These characters and others cross paths over a few days in the city.