Here, I must first explain the history of Deepwater City.
Deepwater City was not originally a city of humans but of elves and dwarves. Later, due to a conflict between the two, the elves left the city, and the dwarves disappeared without a trace by digging tunnels.
So when humans came to the Northern Land, they were thrilled to find such a fully functional and uninhabited city with no owner—naturally, they claimed it for themselves.
It turns out that the decision of the elves and dwarves was correct; since humans settled in Deepwater City, there have been frequent incidents, with little monsters coming to destroy them every other day.
Okay, I digress.