Sentenced to Be a Hero, Vol. 4 (light novel)

To take back Zeyllent from the Demon Blight, the penal hero unit is ordered to go undercover and infiltrate the city. But with the fate of humanity on the line, what will happen when their plan starts to fall apart? Meanwhile, a terrified young girl newly installed as a saint is ordered to lead the main force into the city. With four powerful demon lords awaiting them in the Second Capital, the outlook is grim. But the greatest threat might actually be human.