Accel World Novel Vol. 19 (novel)

Before Kuroyukihime graduates, Haruyuki makes it his mission to travel to the Castle with Sky Raker and learn the clear conditions of Brain Burst as well as what lies at the pinnacle of the Accelerated World. When they arrive, they are warmly received by the dark silhouette of the dual-bladed swordsman, Graphite Edge! But Haruyuki can't afford to be stopped at this critical juncture. For in addition to finding the answers he seeks, Haruyuki learns that the Castle is home to The Fluctuating Light!