In bowl, whisk miso, mirin, sugar, sake, soy sauce, garlic, ginger, sesame oil and pepper; pour the marinade over steaks. Seal bag and marinate steak at room temperature for 30 minutes or as long as 2 days in the refrigerator.
Remove steaks from marinade; blot dry with paper towels. Grill or broil, turning, to desired doneness.
Notes
I like to also sous vide my steaks at 134F. for 2 hours and then sear on the grill