In a large bowl, combine tuna, sesame oil, sesame seeds, Japanese mayo and salt and mix with a fork.

Mix in cooked rice until thoroughly combined.

Prepare a small bowl of water nearby. With clean hands, wet your hands and take a handful of rice, about 2 tablespoon worth. Squeeze it together and roll into a ball, about the size of a golf ball. Repeat this process for the remaining rice mixture. You should have nine rice balls. Note: if you're preparing this for guests, I recommend using plastic gloves or plastic wrap to shape the balls.