Something of a soft reboot for the series after the initial trilogy and the year of Baccano! novels, Dulalala 4 is a massive return to form.
Headless biker Celtie is surprised by a TV crew on the corner one night; they demand to no why she has no lights or license plate. Assuming they'll never be able to broadcast it, she explains that her bike is actually a horse, and it transforms...on live television. Oops. Before she knows it, there's a ten million yen bounty on her head, and every biker gang in the area is chasing after her...while she's got a dead body in her sidecar.
Meanwhile, a Russian hitman and a serial killer disguised as monster are fighting in a park when they accidentally piss off a man dressed as a bartender, who immediately hits them with a bench. The people that stop to help them recover from their wounds send ripples out through the plot, which covers the same time frame from four different points of view, all ending in the same car chase as Celtie's.
Particularly astounding is the introduction of evil strategist Izaya's deranged twin sisters, who proceed to deal with the bullies at their new school by weaponizing thumbtacks, stealing bras, and starting fires in bookbags, before going back to loudly reading porn magazines aloud in class.
Man, the anime version can't air soon enough.