01 - Combine the daikon, carrots, cucumber, and bell pepper in a large bowl. For extra crispiness, sprinkle 1 tablespoon salt over the vegetables, toss thoroughly, and let stand for 15 minutes. Rinse under cold water and drain completely.
02 - Combine rice vinegar, water, sugar, and salt in a small saucepan. Heat over medium heat, stirring constantly until sugar and salt are completely dissolved. Remove from heat and allow to cool to room temperature.
03 - Layer the vegetables, chilies (if using), garlic, and peppercorns into a clean 1-quart jar or container, packing tightly to minimize air pockets.
04 - Pour the cooled brine over the vegetables, ensuring they are completely submerged. Seal the jar and refrigerate for at least 2 hours before serving. For optimal flavor development, marinate overnight. Consume within 2 weeks.