Koshi Isu is a Japanese restaurant in Sadang-dong near Isu Station that serves udon and donkatsu. Its kake udon and bukkake udon are made with house-made noodles aged for 48 hours, and it also serves thick loin donkatsu. The building's underground parking lot is free to use, and there are seats for eating alone. A wait forms at lunch, so allow extra time when visiting.