He arrived in Japan in Jōwa 14, and returned to the capital the next year, where he was granted the rank of daihōshi 大法師. The next year (849) he began giving initiations to others. Ennin built several halls on Mt. Hiei, most notably the Hokke sōjīn 法華總持院, and in 854 he became the third Tendai prelate, or zasu. He gave the ryōbu initiation to Emperor Montoku in 850, administered the bodhisattva precepts to Emperor Seiwa and to Junnaʼs Empress, and the bodhisattva and sammaya precepts, as well as kanjō to the Empress Dowager. In 866, Ennin was awarded the posthumous title of Jikaku Daishi 慈覺大師. Later, the Tendai school split into the mutually hostile Sanmon and Jimon schools; Enninʼs lineage formed the Jimon faction.

Ennin is particularly important in the development of Japanese esotericism because whereas Saichō and Kūkai both taught a two-fold transmission, Ennin taught a three-fold one. He is considered to be one of the three most important representatives of the Tendai esoteric tradition—Taimitsu 台密, along with Enchin 圓珍 and Annen 安然, having considerably influenced the thought of the latter. His works include the Nittō guhō junrei kōki 入唐求法巡禮行記, the Kongōchō kyō sho 金剛頂經疏, Soshitchi kyō ryakusho 蘇悉地經略疏, and Kenyō daikai ron 顯揚大戒論. 〔慈覺大師傳, 元亨釋書〕

References

Reischauer, Edwin O. 1955. Enninʼs Diary: The Record of a Pilgrimage to China in Search of the Law. New York:  : Ronald Press.

----. 1955. Enninʼs Travels in T'ang China. New York:  Ronald Press.