Cut cucumber and tofu into bite-sized pieces.
Open the tuna can and drain the oil.
Pat the tofu dry with a paper towel, then grill it in a lightly oiled pan until golden. Let cool.
In a bowl, add cucumber, grilled tofu, tuna, and rice.
Mix together soy sauce, sesame oil, and sesame seeds for a sauce, add to the bowl, and combine well.
Serve in a bowl and enjoy.