Dr Sadao, while operating, had a habit of talking to his patients in a friendly manner by addressing them as " My friend ", So, He while operating the American prisoner of war, he addressed him as "My friend".
             The irony about his words is that Japan was as at war with America and being a Japanese, according to facts the American prisoner of war was his enemy.But still he muttered those words, this indicates his dedication towards his job as a doctor.