Wash the rice thoroughly until the water remains clear. Bring rice and 75 ml water to the boil in a closed pot. Turn off the heat and let the rice swell for 20 minutes. Remove the pot from the heat and let the rice steam for another 20 minutes in the open pot. Season rice with vinegar, salt and sugar. Stir wasabi powder with a little water until smooth.
Peel the avocado half, cut into strips of about 6 cm and sprinkle with lemon juice. Cut surimi into thin strips (6 cm long) as well. Cut seaweed leaves into quarters. Place a quarter of each leaf in the palm of your hand, spread some rice on top and brush with wasabi. Place a strip of avocado and surimi on top of each and roll up into a bag from one side. Dip in soy sauce before eating