In 2020, the limits of virtual reality were broken after the release of the DreamCaster. Five years later during a game's beta, a leak was found which it resulted of 300 players with amnesia with one player unable to get out. Now in 2030, a player named Kazuma returns to the fully released game after a two year expulsion, along with new and old friends and enemies, must embark on a quest to find his long-lost sister with 100 bosses along the way. On a journey full adventure, laughter, romance, and mystery; will Kazuma find what lies behind the doors of the game known as S.o.L. Online?