Dragon Roll

Name: Dragon Roll
Prep time: 20 min
Total time: 20 min
Cuisine: Asian, Japanese
Ingredients: 2/3 c. sushi rice; 2/3 c. water, plus more for rinsing rice; 1 (2") piece kombu (optional); 1 tbsp. unseasoned rice vinegar; 2 tsp. sugar; 1/4 tsp. kosher salt; 1 qt. vegetable oil; 1/2 c. (or more) all-purpose flour; 1/3 c. (or more) water; 1 large egg; 4 jumbo shrimp (2.5 to 3 oz.), peeled and tails removed; 2 sheets nori; 1 avocado, half sliced 1/4" thick, half very thinly sliced, divided; 1 Persian cucumber, seeds removed and julienned, divided; 1/2 mango, very thinly sliced; 2 tbsp. mayonnaise; 1 tsp. sriracha; Black sesame seeds, soy sauce, wasabi, and pickled ginger, for serving