A/N: Completely AU at this point. What if Brain Burst is an MMO death game, and acceleration is left out for the moment? I own nothing but this story.

== Prologue ==

Above a moonscape reflecting the real-life Tokyo city, a castle floats in the sky.

The castle is named 'Aincrad', and the moonscape below is simply named 'Unlimited Field'.

The castle has ten floors, tapering to its narrowest at the top. But each one is huge. The bottom floor took a group of ten speed-type avatars to map completely, and the final calculation was 10 kilometres in diameter. Large enough to fit Setagaya County inside it. And the Unlimited Field beneath it is even larger, far too large to even see the borders. If any exist. Some have guessed it goes on to map the entirety of Japan, but no one had managed to see it for themselves.

Every player started from Level 1, and the Game Clear condition was to reach Level 10. Each player started with Burst Points, consumed by losing duels, dying, and other ways as well. If one's Burst Points reached zero, he will die a painful death by having his brain fried.

That is to say, this game is a death game. And it has been going on for three years now.

The name of this game- is «Brain Burst Online»

== Login ==

Kirigaya Kazuto
Kirigaya Residence

The time is 12.55pm.

I sighed deeply in the simple wooden chair once more. "So close, yet so far," was the one coherent thought I could discern amid the butterflies in my stomach; After all, today was the day that the revolutionary Virtual Reality Massive Multiplayer Online game, Brain Burst Online is being released to huge fanfare. I looked up from my magazine to the computer screen; the livecast showed a group of teenagers, one not much older than myself and sporting a gaudy bandanna, waving his copy of the game at the camera.

Turning my attention back to the magazine, I flicked past a few full-page advertisements, barely listening to the high-pitched trill of the livecast speaker. Stopping on a well-thumbed page, I gazed at the image of the man seated calmly, his sandy hair cut short and spiked in front.

This was the man behind everything. The next-generation of virtual reality that had taken a huge leap from 3D images to another world. Kayaba Akihiko, the man who invented Full Diving and the equipment needed to use it: the Nerve Gear.

I looked over at the steel-gray helmet resting on my pillow, with a conspicuous wire running from its back to the side, and into the high-speed optical outlet installed in the wall. The Nerve Gear helmet, the only piece of equipment required to play FullDive. The butterflies in my stomach seemed to be mollified by the mere sight of it, even. But then again, it is because that helmet is the gateway to my world.

The time is 12.59pm. I can't wait any longer.

Thumbing the screen of the computer to stand by, I extracted the game disc from its case and slapped it into the side of the Gear. Lying down on my bed, I quickly placed it over my head, letting the half-visor cover just enough light from the window, but can still see the digital clock on the side. I felt around with my left hand for a bit on the low desk next to the bed, and found what I was looking for: a bottle of water and some light snacks, enough for a two, maybe three-minute break between Dives.

"Kazuto, I'm going for practice! See ya later!"

That is my younger sister, Kirigaya Suguha. She's just a little younger than me by about two years. Sugu, as I like to call her, goes for kendo training thrice a week. She is fit, that is for sure. Fitter than me in the real world, and as a swordswoman maybe.

But in the world I am about to enter, I am the strongest swordsman. In that world, I am the swordsman.

The digital clock changes to 13.00. The wait is over, and I close my eyes. There is darkness for a moment.

"Link start!"

Nothing...

Black space turned white.

The login screen appeared, and I quickly logged on. Then, a new window appeared:

Beta Test Character Data detected in Savefile. Use? Y/N

Without hesitating, I hit Y on the virtual keyboard. The screen flashed and disappeared.

Why do I have this data? It is because, two months ago, the 'Accel Assault Online Closed Beta' was held. For two months, a hundred people received the game for free, and had to do all sorts of tests. Skills mechanics, testing for environmental glitches, any possible methods to 'farm' and gain Burst Points quickly. Most people did those, and all of us were paid a token sum of 1000 yen each.

What I did, though, was to Dive everyday for those two months, revelling in the speed and power I didn't have in the real world. In that world, I was the 'Black Swordsman.' A humanoid avatar with an all black coat that wielded a single one-handed sword. Yet, with that one blade, I had climbed all the way up from Level 1 to Level 4, and received the permission to exit the floating castle of Aincrad and able to teleport to the Unlimited Field some twenty kilometres below us. Unfortunately, by then it was two months, and I did not have enough time to explore that map.

The view cleared, and faded to black. My senses returned, and I regained the feeling of having my eyes shut, as they were when I initially Dive. Slowly, I blinked, and opened my eyes to a bright daylight scene.

Cobblestoned pavement, baked brown by the sun. A large fountain in the middle of the plaza, with incredibly detailed water droplets splashing around in it. I held up my right hand and clenched it: the pure black wrist parts rasped with metallic sounds and followed my every command.

In front of me, several pillars of light spawned and faded. More avatars appeared, in various colours, shapes, and types. I glance at the health gauge in the upper left corner of my vision as a last confirmation:

Black Swordsman

HP: 1000/1000

SP: 0%

I pumped my fist once.

"I...I am back in this world!"

tbc.

Author's notes:

That's all for the moment. I'm sticking to the anime events of SAO for awhile, before I bring in the Accel World mechanics in the next chapter. I will note at the beginning whenever I'm referring to LN content as the basis.