I Surrendered My Sword for a New Life as a Mage: Volume 4

After Sylvia’s brush with death serves as a wake-up call, Soma’s party members come back to school with a renewed determination to improve themselves and avoid repeating their careless mistake. But why was there a trap where there shouldn’t have been in the first place? As Soma investigates, he learns of the dark force secretly lurking within the dungeon—and that the academy officials don’t have it nearly as under control as they thought they did.

[From J-Novel Club]