Board Thread:Questions and Answers/@comment-90.221.228.185-20150511233505/@comment-3014077-20170423194829

16.5 isn't canon. What happens in 16.5 stays in 16.5.

The Material Editions commonly referred to as Sugary Days ARE canon, and they answer this question pretty definitively.

Or use the "Reasonable Man" filter. Kirito proposed marriage to Asuna and she accepted. They were married in accordance with the "laws" of the place where they were living. They then spent two weeks on their honeymoon. They were publicly living together as husband and wife. (Remember, they had Nishida over for dinner one night.) What would a reasonable man assume about their relationship?

A more debatable question is have they done it since "escaping" from SAO, in either the virtual or real worlds?