According to the Dharma, ascetic training of the Three Mysteries (the Secret of the Body, i.e., making symbolic gestures with the fingers; the Secret of Speech, i.e., reciting Shingon; and the Secret of Mind, i.e., visualization of the Buddha in the Mandala picture) leads to integration with the main image and Sokushin Jobutsu, which means that one becomes Buddha with one's present physical body.
三密（（身密・手に諸尊の印契（印相）を結ぶ）、（口密（語密）・口に真言を読誦する）、（心密・心に曼荼羅の諸尊を観想する））の修行により、本尊と一体となり、即身成仏が実現するとしている。