Board Thread:General Discussion/@comment-31059495-20170413110502/@comment-25979511-20170415052542

Yes, so the Rio event both happened and didn't happen. It's not novel canon, but it's anime canon. Generally people will enter the events of all the media sources under some sort of umbrella and accept all of it. But if you want to be very serious and strict, the novels are 'the' canon and nothing else (like the Rio event) actually happened...

''Side note: In the novels, Rio isn't actually introduced until volume 7 or so! ''

Conclusion: The novels are indisputably canon. If you ever want to know if an event or conversation between characters is canon, ask yourself: 'was it in the novels?', if not then no. It's not canon.