Finely chop the aged kimchi.
Stir-fry the kimchi in a pan with oil.
Drain the tuna and set aside.
Mix the tuna well with mayonnaise.
Season the rice with salt and sesame oil and mix.
On a bamboo mat, layer seaweed, rice, kimchi, and tuna mayo in that order.
Spread the ingredients evenly and roll tightly.
Cut into bite-sized pieces.