Wash cucumbers under cold water, then thinly slice them using a sharp knife or mandoline. Slice onion into thin strips, sprinkle cucumber slices with salt, and let them sit for about 10 minutes.

In a mixing bowl, soften cream cheese, then whisk together with mayonnaise until smooth. Gradually incorporate soy sauce, rice vinegar, and sesame oil until emulsified.

Pat cucumbers dry with a paper towel. In a large mixing bowl, toss cucumbers and onions with half of the creamy dressing. Allow to sit for about 5 minutes.

Add optional proteins such as imitation crab or shrimp, and fold in the remaining dressing until evenly coated.

Refrigerate for at least 15 minutes before serving to allow flavors to develop. Add garnishes before serving.