Drain the oil from the canned tuna using a sieve. If preferred, you can keep the oil.

Finely chop half an onion.

In a pan, add the chopped onion, 3 tbsp green onion, 1/2 tbsp minced garlic, and 1 tbsp cooking oil. Stir-fry over medium heat for about 30 seconds.

Add the canned tuna to the pan and stir-fry for another minute. Turn off the heat.

Add 5 tbsp water, a pinch of black pepper, 1 tbsp mirin, 1 tbsp soy sauce, 2 tbsp corn syrup, and 6 tbsp gochujang to the pan. Mix well.