Coincidentally, the day Asuna Yuuki, a third-year junior high school student, puts on her NerveGear and enters the VRMMO (Virtual Reality Massively Multiplayer Online) game, Sword Art Online, is the same day it is about to be changed forever.

The game master announces “This is not just a game.” If you die in the game, you die in real life. After hearing this, the players are sent into a state of confusion and pandemonium breaks loose. Among them is Asuna, but without knowing the rules of the world, she embarks towards the iron castle floating in the sky—Aincrad.

While fighting to survive in this world with death ever so near, she has fateful encounters and also farewells. She is at the mercy of the reality at hand, but as she continues to fervently fight, the lone swordsman Kirito appears before her.