Dr. Sadao encounters with the dilemma-to live as private individual whose & moral ethical responsibility is to save the soldier & second is a Japanese to make the soldier arrest.
So as a doctor and as an individual his first job is to save man-takes ethical responsibility, he risks his life, fame & social status- takes him to his house and makes efforts to save him.
But his other side-sense of patriotism & nationalism also involves a report to police, takes the general in confidence, & plans to make him killed but later on again helps the soldier in escaping off. Thus Dr. Sadao personality is displayed.