The Demon Sword Master of Excalibur Academy, Vol. 8 (light novel)

A dead man has returned, bringing the full force of the Azure Fort to bear against Leonis and Veira. And although the two Dark Lords fight bravely, even gaining the upper hand for a moment, they are ultimately bested. The power of the ancient structure sends them to another world. Riselia and the other girls, left behind in Camelot, have no choice but to enter the Holy Sword Blade Dance Festival without their youngest member. The event is far more than it seems, however. A gathering of humanity's greatest Holy Swordsmen is sure to attract nefarious attention...