Shinran (1173–1263) lived at the peak of the ecumenical movement between esoteric and exoteric Buddhism in early 13th-century Japan. In particular, the Tendai school initiated the theological idea of ‘Kenmitsu Icchi’ (the unification of esoteric and exoteric Buddhism), claiming that the Dainichi Nyorai (the central figure of esoteric Buddhism) is identical to the Buddha Shakyamuni (the central figure of exoteric Buddhism). Pure Land Buddhism developed under the heavy influence of Kenmitsu Icchi. Shinran, who spent twenty years studying Tendai philosophy, is likely to have been heavily influenced by the major intellectual trend at that time. However, very few scholars have referred to the fact that Shinran’s doctrine was substantially influenced by esoteric Buddism. Shinran’s doctrine was always focused on ‘Nembutsu’, and is most clearly defined in the chapter on ‘Gyokan’ (practice) in his text entitled Rokujishaku. I have carefully examined the chapter and have found evidence that Shinran believed that Dainichi Nyorai and Shakyamuni were identical. Specifically, his ‘Nembutsu’ ideology was in the same line as ‘Hosshin Seppo’ (the preaching of Dharmakaya) introduced by Kukai, the founder of Japanese esoteric Buddhism.