Accel World, Vol. 19 (light novel): Pull of the Dark Nebula — Reki Kawahara

Prepare for a full dive!
For as long as anyone can remember, Kuroyukihime's one true goal has always been the same: clear Brain Burst and uncover the truth of the Accelerated World. Hoping to help her realize this goal before her graduation, Haruyuki breaks into the Castle where he is reunited with Graphite Edge and Trilead Tetroxide. It is they who ultimately reveal the truth of The Fluctuating Light-Brain Burst's best kept secret-to Haruyuki. And with this newfound knowledge, the last piece falls into place for the combined forced of the Black and Red Legions to confront Oscillatory Universe. The final battle draws ever closer!