Finely chop aged kimchi and onion.
Drain the oil from the canned tuna and prepare.
Stir-fry aged kimchi, onion, and tuna in a pan.
Mix rice with salt and sesame oil evenly.
Spread the seasoned rice evenly over the seaweed sheet.
Place sautéed aged kimchi and tuna, pickled radish, and carrot on top of the rice.
Roll the gimbap and slice into bite-sized pieces.