Bring rice and water to a boil uncovered. Then lower heat and cover and cook for 15 minutes. Then remove from heat and let rest for 10 minutes.
Combine vinegar, sugar and salt in a small bowl. Place rice in a mixing bowl and pour vinegar mixture over rice. Mix well so that all the rice gets mixed. Then let rice cool before rolling sushi.
Mix tezu ingredients together in small bowl.
On sushi roller, place sheet of nori shiny side down. Place about a cup of rice on nori. Dip fingers in tezu mixture so rice does not stick to fingers. Using fingers, spread rice to all four corners.
Sprinkle sesame seeds on rice.
Flip nori around. Lay crab, mango, cucumber and avocado lengthwise in the front of nori. Then roll.
Cut roll into 8 pieces.
Repeat to make two more rolls.