So Luna gets trapped inside a new VRMMO along with thousands of other ponies. Nopony can leave, only enter. 300 elite gamers enter the game, thinking that the game must be beaten in order to free everypony. Celestia finds out that the real way to save everypony is to find Luna, because if the game is beaten, the plug is pulled and everypony in the game will die.

To clear up confusion, this fic was inspired by SAO