I always knew Simon would come through by the end of the series: The one time he decides to finally do something, it is for a perfectly worthy cause. Izaya isn’t really humiliated (save for a mocking laugh thrown his way by Namie), but a nice shiner — along with what has to be several bumps and bruises after flying through the sky courtesy of Air Simon — is some decent comeuppance for 24 episodes of dickery on Izaya’s part.
And yet it also shows a lot of what goes wrong in the second half of Durarara!! Characters with craploads of potential come and go without doing very much at all. Simon sells sushi without affecting the plot much at all, even though he can clearly make things happen. Shingen makes a cameo as if he is appearing in some low-rent sitcom. The cop’s appearance is great, but he probably could have been a more substantial character than he actually is. And on and on and on.