Sword Art Online 8 (light novel‪)‬

The saga of Sword Art Online continues with three side stories set during the Aincrad and Alfheim eras. The game of death took its toll on every player in a different way--when one turns up dead on the fifty-seventh floor, the game's afoot, and it's up to Asuna and Kirito to crack the case. There's also the story of how Kirito got his Excalibur sword in Alfheim (with a little help from his friends). And when the game of death first began, Kirito learned a difficult lesson--one he would never forget.