Prepare the filling - In a bowl, mix all filling ingredients together. Set aside.
Cook the rice - rinse the sushi rice thoroughly under cold water until the water runs clear.
(Optional) Soak the rice in water for at least 1 hour or up to 12 hours. Soaking will result in softer rice, perfect for jumeokbap.
Drain and discard the soaking water.
Cook the rice in your rice cooker as per usual. For 2 'rice cooker' cups of rice, use 2 ½ cups of water - rice:water ratio should be 1:1¼ (Note 4).
Once cooked, transfer the rice to a bowl and let it cool until it's easy to handle.
Assemble - Put on plastic gloves to prevent the rice from sticking to your hands. Grab about 2 tablespoons of rice and shape it into a ball. Flatten the rice ball in the palm of your hand and place about 2 teaspoons of tuna filling in the center. Wrap the rice around the filling, adding more rice on top if needed to seal it completely. Shape it into a ball and press to ensure it holds together.
Place some furikake in a bowl. Roll each rice ball in the furikake to cover the whole surface.
Serve - Serve at room temperature and enjoy as a snack or part of a meal.
