This work provides a survey and critical investigation of the remarkable century from 1225 to 1325, during which the transformation of the Chinese Chan school into the Japanese Zen sect was successfully completed. The cycle of transfer began with a handful of Japanese pilgrims traveling to China, including Eisai, Dōgen, and Enni, in order to discover authentic Buddhism. They quickly learned that Chan, with the strong support of the secular elite, was well organized in terms of the intricate teaching techniques of various temple lineages. After receiving Dharma transmission through face-to-face meetings with prominent Chinese teachers, the Japanese monks returned with many spiritual resources. However, foreign rituals and customs met with resistance, so by the end of the thirteenth century it was difficult to imagine the success Zen would soon achieve. Following the arrival of a series of émigré monks, who gained the strong support of the shoguns for their continental teachings, Zen became the mainstream religious tradition in Japan. The transmission culminated in the 1320s when prominent leaders Daitō and Musō learned enough Chinese to overcome challenges from other sects with their Zen methods. The book examines the transcultural conundrum: how did Zen, which started half a millennium earlier as a mystical utopian cult primarily for reclusive monks who withdrew from society, gain a broad following among influential lay followers in both countries? It answers this question by developing a focus on the main mythical elements that contributed to the overall effectiveness of this transition, especially the Legend of Living Buddhas.