Cut the hairtail, radish, and onion into bite-sized pieces.
Place the radish slices on the bottom of a pot.
Put the prepared hairtail pieces on top of the radish.
Mix gochujang (Korean chili paste), gochugaru (Korean chili flakes), soy sauce, minced garlic, sugar, cooking wine, and black pepper to make the seasoning sauce.
Evenly spread the seasoning sauce over the ingredients.
Add onion, green onion, and Cheongyang chili peppers on top.
Pour water or kelp broth and simmer over medium heat.
Boil until the radish is cooked and the sauce thickens.