Sword Art Online: Mother's Rosary Vol. 3 manga

After Yuuki and the rest of the Sleeping Knightsshared a victory over the Floor Boss with Asuna and left their names on theMonument of Swordsmen, Yuuki mysteriously disappears. When Asuna attempts tomessage her, she finds that she's offline. Desperate to see her once more, sheturns to Kirito, who happens to know exactly where she is and gives her anaddress.But she may come to regret indulging her curiosity...