The Demon Sword Master of Excalibur Academy, Vol. 6 LN

When Leonis and the rest of the eighteenth platoon return from their mission to
Necrozoa, Riselia hammers him with questions about his past. Is it time for him to
reveal his true identity? Meanwhile, a group of armed mercenaries from the Sakura
Orchid plot to invade the Seventh Assault Garden. To stop her former compatriots,
Sakuya will have to seek out the power of a Dark Lord (Leonis)!