>>17 OH Volume 13...~ really, I'd recommend reading it to understand what really happens because summarizing the details of the fight, and the novel overall, causes a total loss of eloquence. However, you can get the gist of the fight on the DRRR!! wiki. What's more confusing and in my opinion requires a little more thought is what happens to Izaya afterward.
On the wiki, you have a couple of options. The entire novel is summarized
here, but if you're only looking for the fight itself, go to the Volume 13 section of
Izaya's page.
(Read Volume 13
here, btw, if you're looking for a complete translation)