Board Thread:News and Announcements/@comment-6697950-20150511150240

As some may have heard, the limited edition 9th volume of the season 2 anime blu-rays and DVDs will include a special side story written by Kawahara Reki. The title for the side story has been revealed to be "Sister's Prayer" and judging from the 21 page preview available on the official site (http://www.swordart-online.net/package/2_vol9.html), the story will be about Yuuki, her sister and the Sleeping Knights before the Sleeping Knights came to ALO.

For those who can read Japanese or are interested in the other bonuses, please see https://www.aniplexplus.com/itemDViKkbQr

Edit: According to Kawahara Reki, the story is about Yuuki, Yuuki's sister and Merida, the first Sleeping Knights member, so the remaining members of the Sleeping Knights might not get an appearance. 