Sword Art Online is a Japanese light novel series written by Reki Kawahara and illustrated by Abec. The series follows the story of a young man named Kirito who becomes trapped in a virtual reality video game called Sword Art Online. The game requires players to complete 100 floors of a tower in order to escape, but if they die in the game, they also die in real life. As Kirito and his friends progress through the game, they face various challenges and encounter other players who become their allies and enemies. The series has been adapted into multiple anime series, manga, and video games, and has gained a large following worldwide.