''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

for my stomach in a sharp arc, a brilliant orange curve flashing through the air. “Fell Crescent” was a high-level heavy attack skill for curved swords, a deadly charging blow that covered a distance of four yards in just 0.4 seconds.

But I knew it was coming.

Keeping my distance was the entire plan—I was daring the enemy AI to use it against me. The scimitar blade passed just inches from my face, my nose wrinkling at the charred odor left in its wake. I ducked, pressing up against the lizardman’s belly.

“…Seya!”

With a cry, I slashed my weapon sideways. The blade, glowing cyan, sliced through the scales of the creature’s soft underbelly, spraying beams of crimson light in place of blood as a dull grak! sounded from above.

But my combo continued unabated. The system automatically assisted my further assault, chaining into the next attack faster than I could have moved on my own.

This is the advantage of sword skills, the most significant and decisive feature of battle in this world.

As the sword leaped back from left to right, it found purchase in the lizardman’s chest again. I followed that momentum into a full-body spin and drove my third blow even deeper into the enemy’s core.“Urarrgh!!”

No sooner had the lizardman regained mobility than it let out a roar of rage and fear, swinging its scimitar down from on high.

But my combo wasn’t over yet. From its full extension to the right, my sword shot diagonally left and upward like a spring, directly striking the enemy’s heart—its critical point.

This four-stroke combination left a square of glowing blue lines extending outward from me: Horizontal Square, a four-part sword skill.

The brilliant light reflected off the walls of the labyrinth, then faded. At the same time, the HP bar displayed above the lizardman’s head vanished without a trace. As it unleashed a long, final scream, the massive green form threw itself backward, paused at an unnatural angle—

And exploded into a mass of delicate polygons with a blast like the shattering of a huge glass structure.

This is death in the virtual world. Instantaneous and simple. Utter annihilation without a trace.

A purple font in the center of my view popped up, listing my experience and item rewards. I swiped my sword back and forth before returning it to the sheath over my shoulder. Backing up several steps to rest against the wall of the dungeon, I let myself slide to a sitting position.When I released the breath I’d been holding and shut my eyes, my temples began to throb dully with the fatigue of the long fight. I shook my head several times to clear the pain before opening my eyes again.

The clock display in the lower right-hand corner of my vision showed that it was already past three in the afternoon. If I didn’t leave the maze soon, I’d never get back to town before dark.

“…Better turn back,” I muttered to no one in particular and slowly rose to my feet.

It was the end of a full day’s worth of “progress.” Another day of successfully eluding the Grim Reaper’s grasp. But once I returned to my bed and took a short rest, the next day would bring another endless series of battles. And when the combat is endless and the stakes are fatal, all the safety nets and backup plans in the world won’t prevent Lady Luck from betraying you at some point down the line.

The only real issue was whether or not the game would be “beaten” before I could draw the ace of spades.

If survival was your top priority, the smartest play would be to remain in the safety of town until the day someone else beat the game. But the fact that I spent every waking moment testing the front line on my own, risking death for ever greater statistical rewards, meant one of two things: that I was either a tried-and-true VRMMO (Virtual Reality Massive Multiplayer Online) addict…

Or a damned fool so arrogant as to honestly think he could free the world with his sword arm.

As I started making for the exit of the labyrinth, a self-deprecating grin tugging at the corner of my mouth, I thought back to that day.

Two years ago.

The moment that everything ended…and began.

2

“Ngh…arrg…hyaa!”

The strained cries were paired with desperate sword swipes, the blade swishing through nothingness.

The blue boar charged its attacker the next instant, nimbly evading his slashes despite its massive bulk. As I watched the beast’s flat snout throw him skyward to roll across the field, I couldn’t help laughing aloud.

“Ha-ha-ha…not like that. The important part is your very first motion, Klein.”

“Yeow…Hairy bastard.”

As the boar’s attacker—my party member, Klein—rose to his feet swearing, he shot back a pitiful reply in my direction.

“Easy for you to say, Kirito…He can really move!”

I’d only met this man just a few hours earlier, his reddish hair flared back by the bandanna tied to his forehead, his lean figure clad in simple leather armor. If we’d introduced ourselves with our real names, it would have been hard not to use polite honorifics. But these were character names we’d chosen specifically for this virtual world: He was Klein; I was Kirito. Attaching -san to each other here would’ve just been weird.

Noting that Klein’s legs were unsteady and his spill had probably dizzied him, I leaned down to the grass at my feet, scooped up a rock, and held it above my shoulder. The system recognized this motion as the initiation of a sword skill, and the stone began glowing a faint green.

The rest happened nearly automatically. My left hand flashed, and the rock traced a bright arc through the air, striking the blue boar between its eyes as it prepared to charge again. The swine uttered a squeal of rage and turned to me.

“Of course it moves; it’s not a training dummy. But as long as you initiate the motion and get the sword skill off properly, the system will ensure that it hits the target.”

“Motion…motion…”

Klein muttered the word like a spell, waving the cutlass in his right hand.

The beast, properly known as a Frenzied Boar, was only a level-1 mob, but with all the missed strikes and painful counterattacks, Klein’s HP bar was nearly half gone. Dying wasn’t a big deal, since he’d simply revive at the nearby starting town, but we’d have to trek all the way back here to the hunting grounds again. This fight could only last one more round.

I tilted my head in hesitation as I deflected the boar’s charge with my sword.

“How do I explain this…? You don’t just hold it up, swing it, and cut the enemy like one, two, three. You have to pause just enough in your first motion to feel the skill cue up, then kapow! You blast it into him…”

“Kapow, huh?” Klein held his curved sword at mid-level as his handsome features crumbled into a pathetic grimace beneath the tasteless bandanna.

He took one deep breath in and out, lowered his waist, then lifted the sword as though to cradle it on his right shoulder. This time, the system recognized the required motion and his arched blade glinted orange.

“Raah!”

He roared and, in a much smoother motion than before, bounded forward with his left foot. A satisfying shgeen! sound effect rang out as his blade carved a path the color of fire. Reaver, a single-handed scimitar skill, caught the charging boar squarely on the head, wiping out its remaining HP.

The enormous bulk shattered like glass with a pitiable squeal, and purple experience numbers floated before our eyes.

“Hell yeah!”

Klein struck a victory pose, turning to me with a huge smile, his hand held high. I returned the high five and cracked a smile of my own.

“Congrats on your first kill. Just remember, that boar was basically the wimpiest little slime in any other game.”

“Are you serious? I was convinced he was a mid-level boss.”

“Not a chance.”

I returned my sword to the sheath on my back, my smile fading to a wry grin.