Wash perilla leaves thoroughly and slice into thin strips.
Combine soy milk, soy sauce, sesame oil, and vinegar in a bowl and mix well to make the cold noodle broth.
Boil the noodles (somen or buckwheat noodles), then rinse under cold water.
Place the noodles in a bowl and pour the cold soy milk broth over them.
Top with perilla leaves, sliced cucumber, cherry tomatoes, and seaweed flakes to finish.