Winner of the prize "Fundacao Oriente - Embaixador Joao de Deus Ramos" of the Academia de Marinha 2021 This book attempts to depict certain aspects of the Portuguese trade in East Asia in the 16th and 17th centuries by analyzing the activities of the merchants and Christian missionaries involved. It also discusses the response of the Japanese regime in handling the systemic changes that took place in the Asian seas. Consequently, it explains how Jesuit missionaries forged close ties with local merchants from the start of their activities in East Asian waters, and there is no doubt that the propagation of Christianity in Japan was a result of their cooperation. The author of this book attempted to combine the essence of previous studies by Japanese and western scholars and added several new findings from analyses of original Japanese and European language documents.