Step 1: Prepare the imitation crab. Gently pull apart the crab sticks into thin shreds by hand or using two forks. Place the shredded crab in a large mixing bowl.
Step 2: Prepare the vegetables and fruit. Peel and thinly slice the English cucumber, then cut it into julienne strips. Peel the ripe mango and cut it into small, uniform cubes. Add these to the bowl with the shredded crab.
Step 3: Make the dressing. In a separate small bowl, whisk together the Japanese mayonnaise, Sriracha (start with 1 tablespoon and add more for extra heat if desired), toasted sesame oil, and rice vinegar. Season with a pinch of salt and black pepper to taste.
Step 4: Combine the salad components. Pour the prepared dressing over the shredded crab, cucumber, and mango in the large mixing bowl. Gently fold everything together until all ingredients are evenly coated with the creamy dressing, being careful not to mash them.
Step 5: Add the masago. Stir in the masago (capelin roe) until it is well distributed throughout the kani salad. You can reserve a small amount for garnish if preferred.
Step 6: Chill the salad. Cover the bowl with plastic wrap and refrigerate the kani salad for at least 15-30 minutes to allow the flavors to meld and for the salad to chill thoroughly.
Step 7: Serve. Before serving, give the kani salad a final gentle toss. Garnish with thinly sliced scallions or toasted sesame seeds if desired. Serve immediately and enjoy your delicious Creamy Kani Salad!