Mikado's descent into control-freak tyranny is the show's real story, not the gang wars. Watch him convince himself that destroying the Dollars from within is freedom, not power, and you're watching a character study of someone already lost before he knows it. The non-linear storytelling isn't a gimmick here, it's how the show refuses to let you see the full shape of what he's become until you've already accepted his logic.
In Ikebukuro, the lives of the city's residents keep crossing in ways that seem almost fated. Mikado Ryuugamine draws nearer to the exciting life he has always wanted, and sinks further into the city's underside. Having taken full control of a former rival, he uses that power freely, weeding out members of the Dollars to shape the group into what he thinks it should be. The task proves difficult once outsiders start interfering, above all a cherished friend who returns to the picture. Meanwhile, Izaya Orihara still has plans in motion, though a competing information dealer operating in the district keeps getting in his way. With so many threads crossing, fresh chaos in Ikebukuro seems only a matter of time. This second part of Durarara!!x2 blends action, mystery, and the supernatural across 12 episodes.