Fill a pot (large enough for the eggs) with water and bring it to the boil.
While the water is warming up, take a resealable freezer bag, open it wide and sit it inside a bowl for support. Put equal portions of tamari, rice vinegar and water inside the bag and stir until well combined. If you'd like to add some sweetness, add your preferred artificial sweetener to taste.
Once the water in the pot is boiling, gently lower the eggs into the water and boil for exactly 7 minutes.
While the water is boiling, prepare a bowl of ice water. When the eggs have are finished, remove from the boiling water and place them straight into the ice water. This will stop them from cooking.
Let the eggs sit in the ice water for 2 minutes, before gently peeling the eggs. This can be delicate as the yolks are still runny.
Once the eggs are peeled, gently place them inside the bag with the tamari mixture. Arrange them in the bowl until they are submerged in the mixture, seal the bag and place in the fridge.
Let the eggs marinade in the mixture for 2 hours (for a gentle flavor) to 2 days (for a stronger flavor).
Remove the eggs from the bag. The marinade can be used again if you wish. Serve the eggs with a sprinkle of shichimi togarashi, sesame seeds or black pepper on top.