The journey from the DMZ to the outskirts of Seoul was not a long one. I mean, it was well within the range of North Korea artillery, which had been a major concern of the South Korean government prior to the collapse of human civilization as a whole.
And that would still be a large concern for anyone who stilled lived within Seoul's borders, considering the fact that North Korea still existed as a political entity, and the DMZ was more fortified now than ever on their side.
Whether or not anyone was left alive in this wasteland of a city, Zane honestly did not know. It was not unusual for human settlements to exist in some limited capacity within the ruins of old world cities. But such an idea was predicated on the situation in America.