Board Thread:General Discussion/@comment-31059495-20170413110502/@comment-25979511-20170415172853

Actually, if you look at it like that then the Rio event still isn't canon. Izaya never met Rio so he failed to have that influence on him which means she never tried to kill herself and therefore was never rescued by Celty and thus influencing her in some shape/form. It contridicts the first half of the novels and the line about Manami having more reason than anybody else to hate Izaya.

It's generally accepted that perhaps the Rio event happened sometime between Manami and others, but there's no canon proof. Theory goes that the Rio event was forced into the anime as a way of showcasing Izaya's antagonistic qualities.

But, if we want to be very simple about this. I'd suggest viewing the novels as the only true canon source considering we have MiniDura, the manga, the anime, and all side manga's not written by Nartia, plus crossovers. That's just if we want to be very safe and sure. I don't think it really matters if you want to view it all as canon or not as long as you don't use them to push a particular agenda *cough* or ship *cough*. Most things can be loosely explained away anyway (contridictions to the novels I mean), just leave it under the umbrella of Durarara, enjoy the story instead.