Board Thread:Editor Board/@comment-6697950-20131220222009/@comment-6697950-20131228181841

I'm saying that the Progressive manga is kind of a main manga, although it tells the story from a different perspective. If we call it a spin-off, then Aincrad one would be a spin-off too.

Personally, anything in the Progressive manga that doesn't conflict with the canon could supplement the canon in my opinion.