Yongsan-gu contains Itaewon — Seoul's most international neighbourhood — as well as the scenic Hannam district and Yongsan Electronics Market. Itaewon's food scene reflects its global community: Indian, Middle Eastern, African, and American restaurants share streets with high-end Korean and Japanese establishments. It's also where many of Seoul's foreign chefs have set up their most ambitious projects.
This is one of the restaurants I recommend for Chinese food. It's located next to Yongsan High School, on the way up to Haebangchon, and has tables on the first floor and in the basement. If you're visiting with family, the jajangmyeon, jjambbong, tangsuyuk, and chadolbaek jjambbong are perfect. Sharing a little bit of the meat-heavy jajangmyeon and the seafood-heavy jjambbong is especially delicious. It's a bit pricey, but the portions are generous, so even a medium tangsuyuk is perfect. They serve refreshing plum tea after your meal, which is perfect for cleansing your palate :)