The Demon Sword Master of Excalibur Academy, Vol. 2 (manga)

After a lively party welcoming Leonis into the eighteenth platoon, he and Riselia visit a nearby orphanage. The kids there are overjoyed to play with their big sister and new big brother...but the fun doesn't last long. A sudden Stampede of Voids stops them in their tracks, and what's more, Riselia is abducted! Now it's up to the reincarnated Dark Lord to take back his minion-and perhaps face off against some familiar faces from his past...