Finely chop the aged kimchi.
Cut the cucumber in half, slice thinly, sprinkle with salt, let it sit, and then squeeze out the moisture.
Remove moisture from the tofu using a paper towel and mash it.
Drain the oil from the canned tuna and prepare.
Place the prepared kimchi, cucumber, tofu, and tuna on top of the rice.
Add gochujang, sesame oil, and sesame seeds, then mix well.