Rinse the rice under cold water until the water runs clear. Combine rice and water in a saucepan and bring to a boil. Cover, reduce heat to low and cook until tender and water is absorbed, 15 to 18 minutes. Remove from heat and let steam, covered, 10 minutes. Fluff gently and cool slightly.
In a medium bowl, toss the salmon with cornstarch, soy sauce, honey and mayonnaise. Heat the oil in a skillet over medium-high. Sear the salmon, turning once, until just cooked through and lightly caramelized, 3 to 4 minutes. Transfer to a plate.
In a large bowl, whisk flour, cornstarch, baking soda, baking powder, salt, pepper and paprika. Add cold water and whisk until smooth. Add the egg and stir just until combined; the batter should remain light.
Heat 2 inches of oil in a heavy pot to 350°F/180°C. Dip each nori square into the batter, coating one side only. Fry until golden and lightly puffed, 30 to 45 seconds. Transfer to a rack or paper towels to drain. While warm, gently bend each into a taco shape; the shells will remain pliable as they cool.
To assemble, spoon rice into each shell. Top with salmon, cucumber, avocado and scallions. Drizzle with spicy mayonnaise and teriyaki sauce. Sprinkle with sesame seeds and serve immediately.