Bring a large pot of water to boil over medium heat, then carefully add eggs to boiling water. Cover and set a timer for 5 minutes and 50 seconds.
While the eggs are boiling, create your marinade. Whisk the warm water and sugar in a small bowl until the sugar is dissolved, then add the soy sauce, saké, and mirin and whisk to combine. Grate the ginger into the sauce mixture and whisk to combine.
Carefully transfer the marinade to a large Ziploc bag or deli cup and set aside.
Prepare an ice bath of cold water and ice. Once the eggs have boiled for the allotted 5 minutes and 50 seconds, remove from the heat and place each egg into the ice bath.
Once cool to touch, peel the eggs and place peeled soft-boiled eggs into the prepared marinade container. Submerge eggs in the marinade, tying the bag closed to keep eggs submerged.
Place eggs in the refrigerator and marinate for 2 to 3 days.
Once eggs are ready they will be deep tan colored. Remove from the marinade and cut in half using a sharp knife. Serve with ramen.
