Ennin (圓仁 or 円仁, 793 CE or 794 CE – 864 CE), better known in Japan by his posthumous name, Jikaku Daishi (慈覺大師), was a priest of the Tendai school of Buddhism in Japan, and its third Zasu (座主, "Head of the Tendai Order"). Ennin was instrumental in expanding the Tendai Order's influence, and bringing back crucial training and resources from China, particularly esoteric Buddhist training and Pure Land teachings. Source: Wikipedia (en)