Slice cucumber depending on your preference. Note: To get the swirl cut, you would use two chopsticks and slice at an angle (video here.)
Mix cucumbers with a generous amount of salt and let it sit for 30 minutes. Rinse well, 2-3 times.
Combine water, mirin, soy sauce, sugar, garlic, wasabi, and sesame oil.
Marinade the cucumbers for at least 3 hours. (Overnight is recommended.)
Sprinkle with sesame seeds when ready to eat.