Mix sugar, vinegar, and salt in a microwave-safe container. Heat uncovered at 600W for 30 seconds, stir until sugar dissolves, and let cool to make sushi vinegar.

Combine cooked rice with sushi vinegar in a bowl, mixing gently to cool and season the rice.

Place a slice of tuna vertically and roll it. Wrap a slice of salmon around it. Repeat to make 2 rolls.

Heat a thin layer of salad oil in a pan. Pour half the beaten egg and spread evenly. Cook until surface dries, flip, and cook for 10 seconds. Repeat to make 2 thin omelets. Cool, then slice one into thin strips and cut the other in half.

Place 1/4 green leaf, 1/6 sushi rice, 1 slice salmon, and 1/4 egg strips on one side of a nori sheet. Roll and top with 1/2 salmon roe. Repeat to make 2 rolls.

Place 1/6 sushi rice, 1/4 green leaf, and one tuna-salmon roll on one side of a nori sheet. Roll and top with 1/4 egg strips. Repeat to make 2 rolls.