Unanswered//butterfly - Sword Art Online

A manga adaptation of Unanswered//butterfly, the feature-length promotional anime for Sword Art Online: Echoes of Aincrad. “This may be a game, but it's not something you play.” Emirun and Rex are caught in a death game where dying in the game means dying in the real world. In a world where even players fight against one another, where will their journey lead them...?