In a mixing bowl, combine soy sauce, perilla oil, and sugar. Stir well until the sugar completely dissolves, creating a smooth sauce.

Bring a medium pot of water to a rolling boil over high heat. Add the soba noodles and cook according to package directions, typically 2-3 minutes.

Drain the cooked noodles in a colander and immediately rinse them under cold running water to stop the cooking process.

Transfer the cooled noodles into the bowl with your prepared sauce. Sprinkle in the Korean roasted seaweed flakes and toss gently.

Optionally top with sesame seeds, chopped green onions, or sliced Cheongyang chili pepper. Serve cold.