Step 1

Combine red chile pepper, green chile pepper, cooking wine, gochugaru, gochujang, soy sauce, brown sugar, garlic, and ginger in a small bowl; mix well to make sauce.

Step 2

Place water and daikon radish in a large pot. Bring to a boil; cook until radish is tender, about 5 minutes.

Step 3

Stir mackerel pieces into the pot. Pour sauce over the mackerel. Cook over high heat, occasionally spooning sauce over mackerel but not stirring the mixture, until cooking liquid has reduced by half, about 10 minutes. Reduce heat and simmer, partially covered, until sauce thickens, about 15 minutes.

Step 4

Garnish mackerel with green onions.