Gather dried seaweed, water, rice vinegar, soy sauce, sesame oil, sugar, sesame seeds, and optional cucumber
Rinse the dried seaweed thoroughly
Soak the seaweed in cold water until softened
Drain the seaweed well
Squeeze out excess water
Slice cucumber thinly if using
Mix rice vinegar, soy sauce, sesame oil, and sugar in a bowl
Add the seaweed and cucumber to the dressing
Toss until evenly coated
Sprinkle sesame seeds on top
Chill before serving