Time flies, and soon it will be a year since the end of the war.
Compared to the humanity of last year, the humanity of today is several times more prosperous and stronger. If the current state of humanity were to face the exact level of threat they had faced a year ago, they would completely eradicate every single one of them, including the Sin Demon King, within two hours.
A lot has changed since then; the most obvious part is the wide open gates leading out to the great expanse of the Azure Terra Continent.
Truthfully, after the initial stages of continental cleansing, if one were to apply for a permit to leave the walls and explore the world outside, the army would've allowed it. The idea wasn't endorsed publicly, but there were certainly a few people here and there who wanted to take their chances.