- In a saucepan, combine water, soy sauce, mirin, sugar, green onion, garlic, and red pepper flakes and bring to a simmer over medium heat. Reduce heat to low and continue to simmer for 5 minutes. Turn heat off and cool mixture to room temperature.
- Place hard-boiled eggs in soy sauce marinade and cover. Refrigerate for 2-4 hours. Marinate for 2 hours if you prefer your food to taste lighter on salt.
- Remove eggs from marinade and slice in half lengthwise. Scoop out yolks and add to a mixing bowl, then mash them into a fine paste with a fork. Add mayonnaise, Dijon mustard and dill. Stir well to combine. Spoon or pipe mixture into center of eggs and top with paprika and chives. Refrigerate until serving.