Rinse the soybean sprouts thoroughly and blanch them briefly in water.
Julienne the onion and carrot, and slice the green onion thinly.
Heat sesame oil in a pan and stir-fry the onion, carrot, and green onion.
Add the tuna to the pan without oil and stir-fry lightly to remove any fishy smell.
Place the blanched soybean sprouts, stir-fried vegetables, and tuna over the rice.
Add gochujang, sesame oil, and sesame seeds, mix well, and serve.