Prep the cucumbers: Slice or chop cucumbers into thin rounds or bite-sized pieces. Pat dry if they’re too watery.
Mix the dressing: In a small bowl, whisk together rice vinegar, soy sauce, sesame oil, sugar, garlic, salt, and pepper. Adjust spice if needed.
Combine vegetables: In a large bowl, toss cucumbers, red onion, and chopped chilies together.
Add the dressing: Pour the dressing over the vegetables and toss until everything is evenly coated.
Garnish & serve: Sprinkle with sesame seeds and fresh herbs. Chill for 5–10 minutes if desired. Serve immediately.