Princess Asmodeus Is in Another Castle

In a desolate land oddly reminiscent of a JRPG, the final boss Beelzebub sits upon a throne with his captive, Princess Asmo, by his side. To save the princess, three adventurers, Leviathan the Hero, Satan the Warrior, and Belphegor the Mage, confront Beelzebub. But when the mighty Leviathan slays Beelzebub with one swing, the adventurers don't receive the reaction they were expecting.