Why is Kaito relevant? Because Eferia has no concept of naval warfare. Their oceans are considered cursed, unnavigable by wooden ships due to sea serpent nests and tidal elementals.
Kaito is rescued by a grizzled Eferian monster-hunter named Sorsha . He learns the brutal economics of Eferia: Mana Cores (harvested from monsters) are currency, and water travel is suicide. He accidentally triggers the Belfast summoning while trying to jury-rig a broken water purifier.
The horizon, for the first time in this waterless world, looks wide open.