"The Returner from the Deep Sea" wasn't something extraordinary...
The reason for its emergence dates back to nearly two years ago, during a time of natural and man-made disasters when the endless ocean suddenly erupted, submerging the world. It was believed to be a catastrophic disaster that would destroy the earth, but unexpectedly, the Deep Sea Era, which submerged almost all the land, did not last long before it gradually receded to its original position...
Humanity then reemerged from various shelters, discovering that the once prevalent calamities and horrors had been cleansed by the ocean like the air after rain...
Although abnormal creatures still existed, they were, at least, not as overwhelmingly numerous as before.
Not long after, people discovered that many individuals who had been submerged were occasionally "spat out" back onto land by the sea.
