Good news! I actually managed to watch this cour of Durarara!! more or less as it aired, instead of mainlining it all about a week before it finished, which was rather emphatically not the case with the first series and with Durarara!!x2 Shou, and which almost certainly coloured my opinions of both of those series.
Picking up shortly after Shou, the second cour of Durarara!!x2 sees Izaya recovering in hospital after having been stabbed by mysterious entertainment mogul/crime boss/monster trafficker Yodogiri Jinnai. Meanwhile, Mikado has become the leader of the Blue Squares, and is using them to purge the Dollars of any undesirable elements; Ruri is being stalked, prompting Kasuka to approach his brother and Celty for help; and the Awakusu Group starts taking a more active interest in the going-ons in Ikebukuro.
As far as starts go, this cour gets off to quite possibly a slower start than the one before, which is odd, in a way - while Shou had to establish new characters and a new status quo after the events of the first series, Ten had all of the groundwork laid by the twelve episodes previous to it with which to get off at a running start, and somewhat squandered it.
|The wholesome ultraviolence gang.|
It does pick up before too long, with the introduction of Ruri's stalker and Masaomi's return to Ikebukuro kicking the plot into high gear by giving the cast a concrete threat, and by providing a catalyst with which to throw Masaomi and Mikado against each other. The stalker plot gets dropped not long after it shows up, but by that point it's already served its purpose, and the tension remains high (and the pacing quick) until the end of the cour.
It's from that point that we also start to see the conflicts set up in Shou really start to pay off. While the gang war at the end of the first series felt like a genuine threat to both the town and its inhabitants, the gang war brewing by the end of Ten feels like that same threat magnified, as the story introduces more and more malevolent parties while putting any stabilising figures out of commission.
Mikado, shown to be well and truly off his rocker by the end of Shou, is terrifyingly unhinged, an effect only enhanced by the cheerful, happy, polite way that he explains to other characters what he's doing (there's a particularly chilling conversation to this effect with Celty in the final episode, where Mikado chirps that he's sent the Blue Squares off to beat up Masaomi's Yellow Scarves) - and the contrast between how he is now, an active participant directing the violence, compared to how he was at the end of the first series, a fairly passive character who continually disavowed any control over the Dollars, is pretty stark.
(He's not the only dangerously unstable character, either, as this cour has seen Aoba's brother Ran, previously only seen briefly in flashbacks in the first series, introduced - and to nobody who remembers what the Blue Squares were doing in those flashback's surprise, he's violent, omni-malevolent, and wants to kill or injure half of the cast.)
|You remember Ran, right? He broke Saki's legs. That Ran.|
Similarly, by having Kadota get caught in a hit and run, Shizuo arrested, and Shinra injured, the series has ensured that, going into the final cour of the series, three out of five of the people who can usually be counted on to keep Ikebukuro safe and stable are out of the action - and their stabilising influence has been established well enough up to this point to make that quite striking for a viewer.
Happily, this cour has also minimised the impact of some of the less interesting characters in the show. The Orihara sisters barely show up at all; Kadota and his gang have a significantly reduced role until the final arc; and Seiji and Mika are mostly absent apart from short appearances to, one supposes, let the audience know that they're still alive. These were always the least interesting characters in the series, so having their involvement scaled back (and the involvement of more interesting characters, such as Masaomi, scaled up) is a definite improvement.
(Less of an improvement is that Anri, as of this point in the series, has been somewhat detached from the main plot for a while, and I do hope she'll get involved in it more in the next cour. That's not to say that she's been absent, though - she's been around in the show plenty, even if it does feel like she's more of an observer than a participant right now.)
|Scary-ish tiny Shinra.|
The cour ends a little abruptly, especially in regards to the Yellow Scarves and Blue Squares storyline, which is just kind of left hanging (as opposed to having some kind of dramatic cliffhanger or somesuch), but the finale does give us some fairly unexpected plot twists regarding the nature of Yodogiri Jinnai and the group he's involved in, and it'll be interesting to see where the show goes with that in its third cour.
All in all, these twelve episodes are much improved over Shou, and I look forward to seeing how everything gets resolved in Durarara!!x2 Ketsu.