Finely chop the cucumber, tofu, and onion.
Drain the oil from the canned tuna and prepare it.
In a pan, add a little oil and stir-fry the tofu, crumbling it as you cook.
In a bowl, add rice, tuna, cucumber, tofu, and onion.
Add salt, pepper, sesame oil, and seaweed flakes, then mix everything together.
Serve on a plate.