Cultural exchange is the most prominent theme in Heart of a Samurai. Due to the stark differences between Japan and America and Japan’s isolation, Manjiro’s entry into American culture is often tense and confusing both for him and others. The characters must learn to interact with one another and understand their differences and similarities. Manjiro’s commitment to learning and adapting to American culture shows this theme, but the balance is unequal. Few characters take the time to learn about Japanese culture in much depth.

The two cultures do not know much about each other. American clothing and food are mysteries to Manjiro and his companions. At the end of the novel, Lord Nariakira says, “Tell me about this country you have been to” (257), revealing that even Japanese elites know little about America. The Americans are equally uninformed about Japan. The cultures are presented as opposites. Customs are different, with politeness in Japan coming across as rudeness in America. Manjiro serves as a bridge between the two worlds. By learning American customs and culture, he can help the two countries begin to come to an understanding.

Manjiro is not bitter that the Americans do not learn much about Japan; he tells them about it when the opportunity arises, such as telling Whitfield about the calendar or Terry about samurai.