From Yen Press:
The once popular game Yggdrasil was supposed to shut down that day. Everyone was supposed to be logged out automatically. But the players who stayed online past the moment the servers went quiet found themselves transported to a game world made real. Leading them is Momonga--a man whose love of games in the real world brought him only loneliness, now a skeletal sorcerer. The legends of Momonga and his guild begin here!