[1][2] Mikkyō is descended most recently from the Chinese Tangmi tradition, especially the dual mandala system taught by Huiguo, itself derived from Indo-Chinese tantric masters such as Amoghavajra.

In older Chinese literature, the term esoteric is used rhetorically to "designate what this or that writer feels is superior or best in the tradition.

Kūkai used a number of other terms for his lineage, such as the "mantra treasury" and kongōjō (金剛乗), literally "vajra vehicle".

[10] Dōshō, Dōji, Simsang, Kaimei, and other clerics introduced esoteric sutras to Japan before the Heian era.

[13] Scholarly approaches to mikkyō often stress the attainment of Buddhahood "in this very body" (sokushin jōbutsu, 即身成佛), or within one's lifetime.

[19] Abhiṣeka (kanjō) is a "ritual of passage" which initiates a student into esoteric practice, based on classical and medieval coronation rites.

Kukai's Precious Key to the Secret Treasury gives a brief overview of the practice: Visualize: a white lotus flower with eight petals, [above which is a full moon disc] the size of a forearm in diameter, [in which is] a radiant silvery letter A. Unite your dhyāna with prajñā in an adamantine binding; Draw the quiescent prajñā of the tathāgata [into your mind].

[26] Ton'a relates a legend (among many circulating in medieval Japan) that Kūkai developed the kana to facilitate the work of carpenters who were building the stupa at Mount Koya.