Together with Saicho (Dengyo Daishi) of Tendai sect, he was positioned at the head of the trend in which Buddhism in Japan had been transformed from the older so-called Nara Buddhism into the new Heian Buddhism, and brought Shingon Esoteric Buddhism to Japan from China.
天台宗の開祖最澄（伝教大師）とともに、旧来のいわゆる奈良仏教から新しい平安仏教へと日本仏教が転換していく流れの劈頭に位置し、中国から真言密教をもたらした。