This article examines the conversion to Christianity of the prince Tayco in the comedia de santos Los mártires del Japón by Lope de Vega and the creation of the Dominican missionary Alonso de Navarrete as a dramatic character. Lope portraits Tayco as a young prince who has to learn how to become a king, having Navarrete as a role model. Lope characterizes Japanese people in ways that are easy to understand for the Spanish public, he also defends the Christianization of Japan.