In a small sauce pot, whisk together soy sauce, sugar and water. Heat the mixture over high heat, bring to a boil, then set aside.

In a separate small sauce pot, heat the wine over high heat until reduced to 1/4 cup, around 4 ounces. Add the reduced wine and miso to the soy mixture and stir to combine well. Let the mixture cool, then pour over the steaks in a nonreactive container, such as a glass pan or resalable plastic bag. Cover and refrigerate for 14 hours, or overnight.

Preheat the grill to medium-high heat. Remove the steaks from the marinade, brush off any excess liquid, and bring to room temperature. Season the steaks with salt and pepper, then place on the grill, keeping the lid open. Sear the steaks on each side, flipping every 2 to 3 minutes. Continue to cook until the steaks reach the desired doneness, about 8 to 10 minutes for medium-rare (with an internal temperature of 135° F).

Remove the steaks from the grill and place on a cutting board. Allow the steaks to rest for 5 minutes, then slice in 1/4-inch slices to serve.