The Wave is gone, but Naofumi's relief is short-lived as Motoyasu challenges him to a duel in the middle of the celebratory banquet held in Melromarc Castle. Motoyasu insists that owning a slave is unbecoming for a hero and that Naofumi free Raphtalia at once.

After hearing of a village that's in immediate need of herbicide, Naofumi and his party head there to do business. The village has been overrun by plants that have turned into monsters, and its residents were forced to abandon it. These plants can even take root in humans, and apparently Motoyasu is the one who released them into the wild.

Naofumi and gang stay on the attack despite being trapped in the Pope's Great Cathedral, but its sacred subspace nullifies his Curse Shield, leaving them one step short. Naofumi turns to another, newly unlocked Curse Shield, but the dragon's wrath threatens to swallow his mind whole.

Melromarc brings a large fleet to fight the Wave out at sea. While the queen takes charge and leads the operation well, the other three heroes prove useless yet again, leaving Naofumi to do it all alone. Later, he gets help from L'arc and Therese to fend off the monsters, but then...