Boil buckwheat noodles and rinse them in cold water.
Julienne cucumber, carrot, and perilla leaves.
Make the sauce by mixing soy sauce, perilla oil, vinegar, plum syrup, minced garlic, red pepper flakes, and green onion.
Add the vegetables and sauce to the cooked buckwheat noodles and mix well.
Drizzle with perilla oil and sprinkle with sesame seeds to finish.