In a bowl, dissolve both sugar and salt in the rice vinegar. Set aside.
Cut the avocados and mangoes in strips. See image above. Set aside.
Wash the rice a few times to get rid of starch that has clung to the grains during the processing. Washing the rice also prevents the rice from clumping. Wash until water is clear.
a) Drain and place the rice in the rice cooker. Add 1.2 cups of water and cook.
b) IF YOU DON'T HAVE A RICE COOKER - Use a regular pot. Bring to a boil, reduce the heat to low. Cover and cook for about 20 minutes.
Place the cooked rice in a bowl and add the vinegar mixture bit by bit. Mix the rice using a 'slicing' or 'cutting' motion.
Place 1/2 sheet of nori shiny side down, width wise on the mat. Moisten fingers and spread about 1/2 cup of cooked rice over the entire sheet, leaving about 1" of nori on top uncovered.
Place a couple or a few sliced avocado and mangoes in the middle of the rice.
Hold the core ingredients with your fingers and with both thumbs, lift the edge of the mat closest to you and bein rolling away from you.
Lift the rolled edge of the mat up to avoid rolling it into the sushi and continue rolling until all the nori is rolled up. Gently squeeze to form a log and removed the mat.
Cut the sushi roll into 6-8 pieces.