1 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»