½ cup finely chopped fresh cilantro leaves, plus more for topping
Red pepper flakes, for topping
Bring a large pot of salted water to a boil. Cook the soba noodles according to the package instructions. Drain the noodles and rinse thoroughly with cold water to remove the excess starch.
Meanwhile, whisk together the soy sauce, vinegar, kimchi brine (if using), and sesame oil in a large bowl. Add the soba noodles, red cabbage, kimchi, scallions, and cilantro. Toss well to combine. Divide the noodles among four bowls and then top with extra cilantro and red pepper flakes.