Boil the buckwheat noodles and rinse them in cold water to drain.
Finely chop the green onion, spicy chili pepper, and seaweed flakes.
In a bowl, mix spicy mayo (Buldak mayo) sauce, perilla oil, soy sauce, sugar, and vinegar to make the dressing.
Add the noodles, dressing, chopped ingredients, and seaweed flakes. Mix thoroughly.
Serve in a bowl and top with egg, mayonnaise, and extra seaweed flakes to finish.