Season hot cooked short-grain rice with ¼ teaspoon salt. Allow this to cool down but keep it covered to prevent the rice from drying out.
In a large bowl, combine shrimp tempura batter ingredients as listed. Add in peeled shrimp into the batter and give it a mix. Set aside.
In small pan filled with 2 inches of vegetable oil, bring to medium heat. Place a wooden chopstick into the oil and when you see bubbles, it’s time to fry.
Carefully lower battered shrimp into the hot oil in small batches. Cook the shrimp on each side for 1 minute until golden brown and crispy.
Remove shrimp from hot oil and transfer to a cooling rack or a paper towel lined plate. Allow the excess oil to drip off to prevent soggy shrimp.
On a clean working surface, rest a ⅓ cup measuring cup. Then lay a large sheet of plastic wrap into the measuring cup. Fill it with seasoned rice until levelled.
Twist the ends of the plastic wrap together to shape it into a triangular ball. Next, poke a deep hole at the top of the triangle with your thumb. Set aside.
In a small bowl, combine Tsuyu soup concentrate and cold water to make the sauce. Dip battered shrimp into the sauce.
Insert the seasoned shrimp into the hole of the rice ball. The rice will break apart here which is normal, so cover the ball with the plastic wrap and shape it back into a triangle.
Next, cut a sheet of nori into 4 equal-sized vertical strips with scissors.
Remove the triangle from the plastic wrap and wrap it with a strip of nori. Serve with more Tsuyu sauce as desired and enjoy!