Marinate chicken in ponzu and lemon juice at least 1 hour, turning occasionally.
For each serving, to order, pat 1 chicken breast dry; season with salt and pepper. Brush with kotteri mirin on both sides. On a gas or charcoal grill, grill on skin side 1-2 minutes or until dark grill marks form. Turn and grill on second side 1-2 minutes. Brush with kotteri mirin; bake in 400°F oven 20-25 minutes or until cooked through, brushing occasionally with kotteri mirin. Cut cross-wise into 1-inch-thick strips with a sharp knife or cleaver.