Combine orange marmalade, mustard, shoyu, melted butter, rosemary, and pepper in a glass or nonreactive container that is just big enough to hold the chicken. Add the chicken to the marinade and coat each piece well. Cover and refrigerate for 6-8 hours, or longer if that’s more convenient.
Remove chicken from the refrigerator and preheat the oven to 400 degrees. If you’re not in a rush, allow the chicken to sit out at room temperature for 30 minutes. Transfer the chicken pieces and any marinade to a baking dish, such as a 13 x 9 - inch. Bake for 45 minutes or until cooked through and browned on top. Remove from the oven and allow to sit for 10 minutes before serving, if possible.