Wow, Durarara!! x2 Shou episode 4 was AWESOME!!!
And also really, really efficient! I didn't think they would get through so much so fast in the anime! The reason the end of this episode might feel especially 'endish' is because they've already reached the end of LN volume 4!
So that completely breaks my initial expectations of season 2 = 3 cours = 3 LN volumes.
If they keep up this pace, they could conceivably get through the entire Akane arc (volumes 5 and 6), Dollars&Squares arc (mostly volume 6) and the Toramaru storyline (woven throughout volumes 4-6) all in this cour which would be totally awesome AND mean we'd still have 26 more episodes of adaptation promised after that! Whoa!
And looking even further... there are 13 LN volumes in the "main series" of Durarara. After that the author started writing "Durarara!! SH" which is like a sequel series - same setting, same style, but taking place a year and a half or so later with new main characters. So... could the anime plan be to adapt all the way to volume 13 by the end of season 2, thereby basically completing the main series? Ambitious but awesome if so, and unlike so many animes that don't manage to get a second/third/xth season and so never reach the ending of their loooong manga/LN series, Durarara having a solid ending at volume 13 and then going into the sequel series means we could get that big ending with season 2 and not need to worry about whether there will ever be a season 3! Soooo excited!
Unfortunately for the twincest fans among you (this is one of those "did I really just write that?" moments), having already completed volume 4 you will not be seeing anymore Mairu and Kururi until at least the Summer cour!
As for this latest episode itself, awesome! Those biker idiots just can't get a break can they - first Kadota, then Celty,
ouch.
There's this whole thing in the LNs about how Igor doesn't need to be inhumanely strong or fast like Shizuo and the supernatural characters (nor is he mentally weird like Vorona and Slon), he's just so skilled that he reacts exceptionally quickly and his every move is so perfectly efficient that he can almost keep up with the supernatural ones. The anime didn't waste time having anyone talk about this explicitly, but they did a great job showing it in the fight with how Igor just slips past enemy attacks and nimbly hits them in the best places with the best timing - totally in contrast to
who was just bashing through everyone with supernatural strength.
Then the yakuza meeting scene - definitely setup for the next arc. Shiki and Akayabashi (the one in the OP, who I can confirm for sure is indeed him now) who we already know were there, and the other two look like Aozaki (the one with tons of facial scars) (though it's hard to say for sure since Mikiya looks pretty similar in the LNs) and the guy with the weirdly round head I am guessing is Kazamoto. Shiki is the only one that is really all that important to the story right now, though it is worth noting that Akayabashi and Aozaki have reputations as super yakuza badasses (I know, I know... who isn't a badass in this series...).
Finally: