This book reveals how St. Francis Xavier’s (1506–1552) dream of evangelizing Japan has been realized by four Catholic missionaries: Aime Villion (1843–1932), Sauveur Candau (1897–1955), Hermann Heuvers (1890–1977), and Georges Neyrand (1920–2011). All of them lived in Japan until death, and wrote and published widely in Japanese for the populace. Their writings are testimony to their endeavors to learn the language, understand the people, and enrich Japanese culture with Christianity. This book re-examines Xavier’s proficiency in Japanese, investigates his influence on missionaries who followed his footsteps to Japan, and explores modern missionaries’ observations of Japan from their insider-outsider perspectives. Their works have fascinated millions of Japanese for their insightful interpretations of Japan and enlightening advice. The literature penned by these missionaries not only enhances our understanding of the five-century long dialogue between Europe and Japan, but also enables us to recognize and appreciate the extremely important role that Christianity has played in shaping today’s Japanese culture.