Goblin Slayer, Vol. 2 (Light Novel‪)‬

Goblins are the weakest of the monsters, with only numbers in their favor. No warrior would dedicate himself to their eradication--except for Goblin Slayer.
As his reputation spreads, a quest comes from none other than the Supreme God's own archbishop--Sword Maiden, the Gold-ranked adventurer renowned for defeating a Demon Lord. The former hero brings a report of goblins beneath the flourishing, peaceful water town, followed by a plea for Goblin Slayer and his companions to investigate, since no one else will. Searching the catacombs beneath the town, though, the party discovers that the trouble runs far deeper than any of them realized. How are all these goblins entering the city? And why is Sword Maiden so desperate...?