1 Chapter 1

''This might be game, But it's not something you play.''

An impossibly huge castle of rock and iron, floating in an endless expanse of sky.

That is the entirety of this world.

A tireless, month-long survey by a team of fanatical experts found that the base floor of the fortress was more than six miles in diameter, just large enough to fit the entire Setagaya ward of Tokyo inside. And considering the one hundred floors stacked one on top of the other, the sheer vastness of the structure beggared the imagination. It was impossible to estimate the total amount of data it all represented.

Inside the castle were several bustling cities, countless smaller towns and villages, forests, plains, and lakes. Only one staircase connected each floor to those adjacent it, and these staircases were located within dangerous mazes filled with monsters. It was difficult just finding them, much less reaching them, but once someone had cleared the stairs and arrived at a major city the next floor up, a teleport gate linking the two floors would open in every city below, allowing all players instantaneous travel among the various levels of the castle.

It was thus that, over two long years, its inhabitants slowly but steadily conquered this giant fortress. The current human frontier is the seventy-fourth floor.

The castle's name is Aincrad, a floating world of blade and battle with about six thousand human beings trapped within. Otherwise known as—

Sword Art Online.

1

The dull gray point of the sword chipped my shoulder.

I felt a chilly hand squeeze deep within my chest as the thin line fixed to the corner of my vision shrank slightly.

That blue horizontal line—my HP bar—was a visualization of my remaining life force. I still had more than 80 percent of my maximum health remaining, but a wiser perspective said I was 20 percent closer to the brink of death.

Before the enemy's blade could begin its motion again, I darted backward to maintain the distance between us.

"Huff…"

I forcefully exhaled and took another breath. My virtual "body" in this world required no oxygen, but back on the other side, my flesh-and-blood form was no doubt panting heavily as it lay prostrate on my bed. A cold sweat would be glistening on my outstretched hands, my pulse racing without end.

It was only natural.

Everything around me was a virtual 3-D object, the only thing I'd lost being abstract, numerical hit points, but my life hung in the balance all the same.

In that sense, this battle was the ultimate injustice. The "enemy" before me—a half-man, half-beast monster covered in slick green scales with long arms, the head of a lizard, and an elonga ted tail—was not only inhuman, it wasn't even truly alive. It was a mass of digital data that could be rebuilt by the system endlessly, no matter how many times it was killed.

Okay, it wasn't quite that simple.

The lizardman's AI program was observing my fighting style, learning my habits, and sharpening its reactions moment by moment. But the instant this individual creature died, that information would be reset rather than carried over to the next lizardman to pop into the area.

So in a sense, this lizardman was alive. It was a unique individual, one of a kind.

"…Right."

It couldn't have understood what I was muttering under my breath, but the creature—a level-82 monster called the "lizardman lord"—exposed the needle fangs lining its slender jaw and hissed a laugh at me anyway.

It's real. Everything in this world is real. None of it is artificial.

I held out the long sword in a straight line, chest-high. The lizardman raised the buckler on its left arm and drew back the scimitar in its right.

As we paused, a chill breeze emanated from beyond the dim labyrinth corridor, rippling the torches along the wall. The flame light flickered off the damp stones.

"Gruagh!!"

With a ferocious roar, the lizardman lord leaped forward. Its scimitar darted