Kimchi Yokocho キムチ横丁
On the other side of the tracks is an area called Kimchi Yokocho. In an area of a few blocks is a concentration of shops and restaurants specializing in Korean food. There is a much larger area filled with Korean supermarkets, restaurants, and shops near Shinjuku near the Shin-Okubo station on the Yamanote line.
Even though the map is in Japanese, it will give you an idea of the number of shops in Kimchi Yokocho and where they are located.