The Jesuits went on to spread the Gospel in new mission fields around the world, but I am particularly interested in how the Jesuits proselytized in East Asia in relation to local religions and beliefs. According to Christian logic, Japanese religions and beliefs are idolatrous and inherently unacceptable. In India and Southeast Asia, European principles of idolatry apply, but we see that in Japan, they are relaxed. Specifically, they actively abstain from the application of Christian law. Thus, the Japanese Christians were conditionally allowed to engage in idolatry. The reverence for the Christian God comes back to the debate about the extent to which idolatry in Japan can be tolerated. Manual de confesores y penitentes, an enormously influential work written by Xavier's maternal great-uncle Martín de Azpilcueta and first published in Portuguese in Coimbra, went through numerous editions and was used as a guide to the conscience and the sacrament of penance. In it, the question of ethics is addressed separately, using the Ten Commandments as the basis that defines Christian ethics concerning God. We see the book used in Japanese missionary work, but problems in Japan often deviate from it, so these problems are discussed as unique to Japan.