Make the Sushi Rice: Wash and rinse the rice with cold water. Add the rice and water to the rice maker. Cook according to the instruction. (You can also cook it in a regular saucepan on the stovetop.)
Once cooked, transfer the rice to a large bowl and let it cool down slightly. When it’s still very warm, stir in the sushi vinegar (or the mixture of rice vinegar, sugar, and salt).
Cut the Octopus: Cut the octopus into thin slices with about 30 to 45 degree angle. I recommend cutting it to 3-inch long, 1-inch wide, and 1/4-inch thick pieces. (You’ll need to adjust the angle from time to time to get the proper length and thickness.) Pat it dry after cutting.
Shape the Rice: Take about 3 tablespoons of rice in your right hand. Squeeze it together until it rolls into a firm oval shape. Try to make the bottom flat with the rounded top. (You can dip your hand in tezu water* to prevent sticking.)
Assemble the Sushi: Place the octopus slice on the root of your fingers. Then take a pea-sized portion of wasabi, and spread in the middle of the octopus.
Place the rolled sushi rice onto the octopus, and bend your fingers to cover both the octopus and rice together. Press down the rice using the index finger from the other hand.
Turn the octopus and rice and let the octopus slice sit on top of the rice.
Cut the seaweed into 1/4- inch strips and wrap each strip around the width of the nigiri. Serve with wasabi, soy sauce, along with pickled ginger.