Wash the buckwheat noodles and vegetables thoroughly and prepare them.
Boil water and cook the buckwheat noodles for 3 minutes.
Rinse the cooked noodles in cold water and drain well.
Place the noodles in a bowl and top with cucumber, seaweed flakes, and green onion.
Mix perilla oil, soy sauce, vinegar, sugar, and minced garlic to make the sauce.
Pour the sauce over the noodles, mix well, and serve.