The Korean Demilitarized Zone (DMZ) can be visited as a guided tour (1 day trip from Seoul), however there are some restrictions, e.g., South Koreans are not allowed go there. So don’t be surprised that your guide is a Japanese woman!
In general, it’s a sad, historical and interesting place for visiting. But please follow the rules while being there, and don’t try to cross the border on your own! DMZ is still a war zone, however by many is treated just as a funny attraction…