2 tablespoons mirin
2 teaspoons white miso
2 teaspoons grated fresh ginger
1/3 cup carrot juice
2 tablespoons fresh orange juice
2 teaspoons low-sodium soy sauce
1 tablespoon plus 2 teaspoons distilled white vinegar
1/8 teaspoon red-pepper flakes
1/4 teaspoon sesame oil
1 scallion, green part only, thinly sliced
3 tablespoons unhulled white sesame seeds
1 tablespoon unhulled black sesame seeds
1 pound sushi-grade yellowfin tuna, cut into 4-ounce rectangular pieces
1 tablespoon safflower oil