Nobu is technically the prince of the nation of Faith Magic in Luxen, but his true position is a bit more complex. He disagreed with the way his family did things and so he left to build a new life and fight against his family. He's a very shrewd individual, and typically fights with his intelligence and agility more than raw strength. I imagine his voice as being somewhat naturally regal, with intonations that make him seem pretentious even if he isn't. It should also be on the higher side. Not super high pitched, more like somewhere in the middle. It can be deep at times, but his natural speaking voice is definitely a bit higher than normal. Nobu is a very important character across the past arc.