1. Bring a saucepan of water to a boil. Carefully add the eggs and cook for 7 minutes.
2. Transfer the eggs to a bowl of ice water and let them cool for 5 minutes.
3. Peel the eggs and set aside.
4. In a plastic bag or container, mix soy sauce, mirin, water, and sugar until the sugar dissolves.
5. Add the peeled eggs to the marinade, ensuring they are fully submerged. Marinate in the refrigerator for at least 4 hours or overnight for best results.
6. Remove the eggs from the marinade, slice in half, and serve with ramen or enjoy as a snack.