Sword Art Online

Prologue

A huge castle made of stone and steel floating in an endless sky.

That was all this world was.

It took a varied group of craftsmen one month to survey the place; the diameter of the base floor was about 10 kilometers—large enough that the entirety of Setagaya-ku would fit on it. Above, there were 100 floors stacked directly on top of each other; its sheer size was unbelievable. It was impossible to even guess how much data it consisted of.

Inside, there were a couple of large cities, countless small towns and villages, forests, plains, and even lakes. Only one stairway linked each floor to another, and the stairways were in dungeons where large numbers of monsters roamed, so discovering and getting through was no easy matter. However, once someone broke through and arrived at a city in the higher floor, the «Teleport Gates» there and in every city in the lower floors would connect, making it possible for anyone to move freely through these levels.

Under these conditions, the huge castle had been steadily conquered over two years. The front line was currently on the 74th floor.

The name of the castle was «Aincrad»; a floating world of battles with swords that had engulfed approximately six thousand people. Otherwise known as...

«Sword Art Online»