Rinse the sushi rice under cold water until the water runs clear. Cook the rice according to package instructions.
While the rice cooks, prepare the seasoning mix by dissolving the sugar in the vinegar.
Once the rice is cooked, transfer it to a non-metallic bowl (bamboo bowl). Gently fold in the sushi vinegar mix and the homemade shrimp stock. Let the rice cool slightly. To make the shrimp stock, add the shrimp shells and 200 ml water to a small saucepan. Bring to a simmer and cook for about 10-15 minutes. Strain the liquid and set aside.