Prepare the marinade by whisking together the soy sauce, honey, grated ginger, minced garlic, rice vinegar, and sesame oil in a medium bowl until well combined. Place the cod fillets in a shallow dish and pour the marinade over them, turning to coat evenly. Cover and refrigerate for at least 30 minutes to allow the flavors to infuse.
Preheat a large skillet over medium-high heat and add the vegetable oil.
Remove the cod from the marinade, letting any excess drip off. Lightly season with salt and pepper. Place the fillets in the hot skillet and cook for about 4–5 minutes per side, depending on thickness, until the fish is opaque and flakes easily with a fork.
During the final minute of cooking, pour the reserved marinade into the skillet and allow it to simmer and reduce slightly, creating a glossy glaze that coats the fish.
Transfer the cod to a serving plate and spoon any remaining glaze over the top. Finish with a sprinkle of sesame seeds and chopped green onions before serving.