Rinse the sushi rice under cold water until the water runs clear. Combine the rice and water in a rice cooker and cook according to the manufacturer's instructions. Once cooked, transfer to a bowl and let it cool slightly.

Season the Rice

In a small bowl, mix rice vinegar, sugar, and salt until dissolved. Pour the mixture over the warm rice and gently fold it in with a spatula. Allow the rice to cool to room temperature.

Prepare the Fillings

Slice the tuna, salmon, and yellowtail into thin strips. Halve the avocado and slice it into thin pieces.

Assemble the Roll

Place a sheet of nori on a bamboo sushi mat. Wet your hands with water to prevent sticking and spread a thin layer of sushi rice over the nori, leaving a 1-inch border at the top. Arrange strips of tuna, salmon, yellowtail, masago, and avocado across the center of the rice.

Roll the Sushi

Using the mat, carefully roll the sushi away from you, applying gentle pressure to keep the roll tight. Seal the edge of the nori with a little water.

Slice and Serve

Using a sharp knife, slice the roll into 6-8 pieces. Serve with soy sauce, wasabi, and pickled ginger on the side.