Prepare rice according to the directions written on the package.

While the rice is cooking, whisk together rice vinegar, sugar, and salt in a bowl and set aside.

After the rice is done, place it into a large, wide, shallow dish. (Avoid using metal since vinegar may react to it.) Pour the vinegar mixture evenly over the rice and mix using a spatula. The vinegar seasoning must be mixed while the rice is hot. As you are folding in the vinegar mixture, fan the rice briskly with hand or electric fan. Continue fanning and mixing until the rice has cooled to body temperature and appears glossy.

Roll Aburaage with a rolling pin a couple of times to flatten them and carefully open each Aburaage to make a pouch.

Make a rice ball filled with tobiko, and stuffed the rice balls in the pouches.