After the wise words of the Green couple, both of them had roughly understood the situation.
There was an area beneath the sea, near the location of Martin Town. Below, there was a stone gate that seemed like nothing more than a useless rock, but upon stepping through it, one would enter a separate space. Interestingly, within that space existed a small, enclosed world, which was very suitable for hiding from the monsters when night fell. However, that space would gradually shrink if someone stayed too long.