Warships in the Deep Sea

Two hundred years ago, on a parallel Earth, a gigantic alien ship fell from the sky. Hundred-meter-tall monsters surged from fissures beneath the sea, and a strange fog shrouded the waters of all five oceans... After fifteen years of desperate resistance, humanity was forced to retreat into the depths of the sea. Two hundred years later, the sea fog remains. The survivors on land, who may no longer qualify as human from a biological perspective, have forgotten the heroes who fought to the very end. Now, whether of their own accord or spurred on by mysterious forces, they have begun attacking the deep-sea dwellers, even at the cost of having their bodies altered... At this moment, can Ren Quan, who accidentally transmigrated here from another parallel Earth, set things right and save this world? Even he doesn't know... . My name is Ren Quan. Ren as in human. Quan as in fist.