Rinse and wash rice until water comes out clear. If you have the time let rice soak in water for an hour.
Cook rice in rice cooker. If you don't have a rice cooker, follow package instructions to cook on stovetop. Or use recipe instructions: place rice and fresh water in a pot over medium-high heat. Bring it just to a boil and reduce heat to low. Cover the pot, and simmer for 15 minutes. Turn off heat and let rice rest covered, for an additional 10 minutes.
While your rice is cooking, prepare rice seasoning. In a small saucepan over medium heat, combine rice vinegar, sugar, and salt. Heat mixture while stirring just until the sugar dissolves (do not let it boil). Remove from heat and set aside until your rice is cooked.
Once your rice is cooked, stir gently with a rice paddle or (wooden) spatula. Pour your vinegar mixture over the rice while you stir, trying to evenly season the rice. Alternatively spread your rice out over a cookie sheet and pour the vinegar mixture evenly over the rice. Turn gently with your rice paddle or wooden spatula.
Evenly divide the rice into 5 parts. Place one part in each of your bowls (or lunchbox) and top with a bed of lettuce. The 5th part is for the cat rice balls.
While the rice is still warm, but not hot, press a couple tablespoons into the cat shaped rice ball mold. Following the instructions of the rice ball kit it will turn into a cat shaped ball in seconds. To keep rice from sticking to your hands lightly water them. Using a food brush give the rice balls cat-like fur markings with some soy sauce. Use the seaweed cutter of the kit to cut out face features like eyes, whiskers and ears. Gently press those onto the rice balls to create the faces. A pair of food tweezers can help you with that. Set shaped rice balls onto parchment to cool down and stick together even more.
Divide all vegetables evenly onto the bowls. Once assembled, top each bowl with cat shaped rice ball to make your bowl kawaii. Drizzle with soy sauce or other sauces shortly before eating.