Board Thread:S,R,&G/@comment-153.150.21.222-20170301065626/@comment-4567891-20170301174838

Like the anon mentioned, Kirito only falls in love with Asuna in LN. Sachi is his friend, not his first love like in the original Web Novels. And yes, Progressive is part of the main LN canon and is only expanding on the events of the Aincrad arc before they reached Floor 75. Events that happened in Progressive are also referenced in later novels and side-stories, so it is canon, even if Reki had retcon some details such as dates and the like, but not to the point where it changed the main story in any significant way.