Peel cucumbers, but leave alternating green stripes. Slice the cumbers in half lengthwise, spoon out the seeds, and then cut into very thin half moons.
Mix rice vinegar, sesame oil, sugar, and salt in a bowl. Stir until sugar and salt are dissolved.
Add the cucumbers and sprinkle with the sesame seeds. I like to eat this immediately for the greatest crunch. However, my mom likes to refrigerate the salad for an hour so that the cucumbers become slightly pickled.