At the opening of the Benkenmitsu Nikyōron (Treatise on the Distinction between Exoteric and Esoteric Buddhism), Kōbō Daishi Kūkai distinguishes exoteric from esoteric teaching. Exoteric teaching takes the practice of the six perfections as its core and teaches that one becomes a buddha over the long span of three immeasurable eons. Esoteric teaching is the teaching in which the Dharma-body Buddha himself expounds the gate of the Three Mysteries of body, speech, and mind. The Three Mysteries are the workings of the Buddha’s body (gestures and mudrās), speech (mantras and words), and mind (heart and meditation). Through sanmitsu kaji, practitioners join their own body, speech, and mind with the Buddha’s. In this way they walk the path of attaining awakening in this very body (sokushin jōbutsu).
In the Hannya Shingyō Hiken (Secret Key to the Heart Sūtra), Kōbō Daishi presents holding the mantra in mind and reciting it aloud as a practice that clears away ignorance (mumyō), the root delusion of the mind, and opens the pure mind we originally possess.
The Six Paramitas can be practiced not only in temple training but also before a family grave or a household altar. An oral tradition handed down in Shingon assigns the six kinds of offerings placed before the Buddha to the Six Paramitas: water (aka) to giving, scented powder (zukō) to discipline, flowers to patience, incense to effort, food (onjiki, such as rice and dishes offered to the Buddha) to meditation, and the lamp to wisdom. We bring the six teachings into the gestures of daily worship, and with the mind we have settled before the Buddha, we go on to meet the people in our lives.