Nanami is a very wise and reserved kind of man, often appearing so calm and indifferent that he comes off as stoic and aloof. He seems like the kind of person who's too serious about his work, but Nanami just knows how to separate sentimentalism from service. He's blunt and straight to the point in most conversations and doesn't care for impractical optimism or questions left open to interpretation.
Additionally, Nanami is very avid and quick to express his irritation, either on his face.