Prepare oatmeal, kimchi, tuna, and green onion.
Finely chop the kimchi.
Add sesame oil to a pot and sauté the green onion and kimchi.
Add the tuna and stir-fry together.
Pour in water and bring to a boil.
Add the oatmeal, stirring as it cooks.
When the porridge reaches your preferred consistency, season with salt and pepper.
Transfer to a bowl and serve.