In a large bowl, combine the sliced cucumbers, shredded imitation crab meat, diced avocado, and sliced green onions.
In a separate small bowl, whisk together the rice vinegar, soy sauce, sesame oil, sugar, salt, and pepper until well combined.
Pour the dressing over the cucumber mixture and gently toss to coat all the ingredients evenly.
Sprinkle sesame seeds on top and give it a final gentle toss.
Chill the salad in the refrigerator for at least 15 minutes before serving to allow the flavors to meld.