Interestingly, Yangyang's O-Il jang ('oh' as in the sound of the letter is five, 'il' is 'day' and 'jang' is 'market') is not on the list. I suppose it is too small, although I have always enjoyed it.
Below is a description of five day markets and the days they run. Yangyang, not on the list, would listed as (4,9 jang) because its market runs on days with a four or a nine.
If you want to learn about five day markets in your region, follow the above link.
For more about Yangyang's unduly snubbed market look here or here.
4. Jeongseonjang (2.7 jang) - Here, the market is also a popular tourist attraction.
5. Donghae Bukpyeongjang (3.8 jang) - This is the largest five-day market in the Yeongdong area.
6. Pyeongchang Bongpyeongjang (2.7 jang) - Tens of thousands of people gather at this market in September when buckwheat flowers bloom.