1 (2-inch-long) piece daikon radish
1 medium carrot
2 tablespoons fresh lime juice
1/4 teaspoon Asian sesame oil
1 (2-inch-long) piece seedless cucumber
1/2 fresh jalapeño, stemmed and seeded
1/2 ripe medium avocado, pitted and peeled
1 tablespoon rice vinegar (not seasoned)
1/3 cup mayonnaise
1 ounce tobiko (flying-fish roe)
1/4 cup bottled yuzu juice
2 teaspoons soy sauce
1 teaspoon Asian chile oil, or to taste
8 (8-inch) round rice-paper wrappers
1 pound crabmeat (from about 3 Alaskan king crab legs), picked over and coarsely flaked
1 scallion, thinly sliced diagonally
8 cilantro sprigs plus 16 leaves