Now over 20 years old, Reki Kawahara's Sword Art Online remains one of the most popular anime and manga franchises in the world, all while being incredibly controversial as well. Many are aware that it got its start as a light novel series, but these books actually began as a web novel published online. There have been numerous spinoffs and adaptations since then, but the main storyline has always been clearly forecast for those who have read ahead with the source material.
Source：https://www.cbr.com/sword-art-online-unital-ring-arc-first-new-content-ten-years/
