Defeating the Demon Lord's a Cinch (If You've Got a Ringer), Vol. 4

The hero’s party is off to the water capital, Cloudburst, in order to contract with more powerful elemental spirits. It’s a big endeavor for even the typical mage, but a necessary one to defeat the Demon Lord. They may have bitten off more than they can chew, but not to worry—priest Ares Crown is close behind, and this time he’s got two powerful mercenaries with him! One way or another, he’ll keep the hero safe, even if it means venturing to the bottom of the ocean! …Unless the Demon Lord’s right-hand man and ruler of the seas has anything to say about that.

[From Yen Press]