Accel World: Acchel World.

Spin-off of Accel World included on the anime Blu-ray/DVDs.One autumn day in 2046, Haruyuki has an encounter with Kuroyukihime, 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 from her, Haruyuki learns of the existence of the virtual Accel World. In that moment, the lowest of the “school caste” becomes “Burst Linker”, a knight defending a princess.