Within the Ryōbu Shintō current, the scriptural heart of practice lies in the esoteric corpus inherited from Shingon Buddhism. Foremost among these are the *Mahāvairocana Sūtra* (Dainichi-kyō) and the *Vajraśekhara Sūtra* (Kongōchō-gyō), which establish the vision of Dainichi Nyorai as the cosmic Buddha and provide the ritual and cosmological framework that Ryōbu Shintō adapts. These two sutras are not merely texts to be read; they serve as the doctrinal wellspring from which the entire symbolic universe of Ryōbu Shintō is drawn, especially in the way kami are interpreted as manifestations of buddhas and bodhisattvas.

Closely bound to these sutras are the two great mandalas of the Womb Realm (Taizōkai) and the Vajra Realm (Kongōkai), often referred to together as the Ryōkai Mandala. Although not scriptures in the narrow sense, these mandalas, along with their ritual manuals, function as authoritative esoteric “maps” that Ryōbu Shintō uses to correlate Shintō kami with specific deities in the Buddhist pantheon. The visual and ritual engagement with these mandalas becomes a means of re-reading the native deities through the lens of esoteric cosmology, allowing the practitioner to move between the world of the kami and the world of the buddhas without contradiction.

In practical terms, this synthesis is sustained by a body of esoteric ritual manuals and commentaries, especially those stemming from Kūkai and subsequent Shingon masters. These works elaborate mantras, mudrās, visualizations, and ceremonial procedures, and they are adapted so that the same esoteric technologies of body, speech, and mind can be directed toward kami worship. Through such texts, the honji–suijaku paradigm—where buddhas are seen as the original ground and kami as their manifest traces—receives concrete ritual expression. Thus, Ryōbu Shintō stands on a foundation in which the *Mahāvairocana Sūtra*, the *Vajraśekhara Sūtra*, the two-realm mandalas, and their associated ritual literature together form a single, integrated scriptural and practical universe.