The Demon Sword Master of Excalibur Academy, Vol. 7 (Manga) - Yu Shimizu

Leonis unexpectedly reunites with his old comrade from a thousand years ago--Veira, the Dragon Lord. To save his friend from the void that's eaten away at her, and to settle their dispute from back before he reawakened, he boldly takes her up in battle! In the legendary clash between Undead King and Dragon Lord, spanning over a thousand years, who will end up the final victor?!