One autumn day in 2046, Haruyuki has an encounter with Kuroyuki-hime, the prettiest girl in his school. For the middle school boy who is often bullied, the meeting changes his life. Through a mysterious piece of software she gave him, Haruyuki learns about the existence of the virtual Accel World. It was after that fateful encounter that Haruyuki of the lowest school caste becomes Burst Linker, a courageous knight defending a princess.
Summary taken from: MyAnimeList