The Demon Sword Master of Excalibur Academy, Vol. 6 (manga)

Leonis and the rest of the eighteenth platoon have returned from the abandoned city, just in time for the Holy Light Festival — a schoolwide celebration jointly held with the Sixth Assault Garden. The dorm’s event of choice? A haunted café, complete with tasty treats and cute costumes—including one for the Dark Lord himself! But even during this relaxing moment, evil stirs beneath the surface, and Nefakess has turned his sights to the silver-haired vampire by Leonis’s side…