Whisk together the gochujang, soy sauce, rice vinegar, honey, and water until smooth and glossy. Stir in the grated garlic and sesame oil.
Pat the peeled medium-boiled eggs completely dry, then add them to the marinade and roll until evenly coated.
Transfer the eggs and marinade to an airtight container, cover, and refrigerate 8–12 hours, turning once halfway through.
Slice the eggs and garnish with sesame seeds, scallions, or shredded nori. For extra sheen, brush a thin layer of leftover marinade over the cut surface.
Store in an airtight container in the fridge: 3–5 days for medium-boiled eggs, 5–7 days for hard-boiled.