Ryōbu Shintō does not rest upon a separate, self-contained canon of its own; rather, it lives in the “between-space” where Shintō and esoteric Buddhism meet and reinterpret one another. Its scriptural foundations are therefore drawn from both sides of this relationship. On the Buddhist side, the Mahāvairocana Sūtra (Dainichi-kyō) and the Vajraśekhara Sūtra (Kongōchō-kyō / Kongōkai kyō) are especially central, since they articulate the cosmic Buddha Dainichi, who is read in close relation to major kami. Commentaries and ritual manuals by Kūkai and later Shingon masters deepen this esoteric framework, and Ryōbu readings use them to articulate a vision in which kami and buddhas are mutually illuminating presences rather than rivals.

From the Shintō side, the classical mytho-historical chronicles Kojiki and Nihon Shoki serve as indispensable sources. Their genealogies and narratives of the kami are not discarded but re-read through a Buddhist lens, so that prominent deities such as Amaterasu can be understood as manifestations or traces (suijaku) of buddhas and bodhisattvas. In this way, Ryōbu Shintō does not so much replace the older stories as draw out new resonances within them, allowing the same myths to speak in a different theological key while preserving Shintō identity.

Around these core scriptures grew a wide body of medieval shinbutsu-shūgō literature that gives Ryōbu Shintō a more explicit doctrinal shape. Tendai-based Sannō Shintō writings and Ise Shintō (Watarai Shintō) materials elaborate honji-suijaku theories that pair specific kami with particular buddhas and bodhisattvas. Shrine-temple (jingū-ji) ritual manuals and engi, the foundation legends of complexes such as Usa Hachiman, Kumano, and Kasuga, likewise systematize these correspondences in liturgy and narrative. Alongside these, various apocryphal and esoteric transmissions further articulate the links between kami and Buddhist deities, even if many such materials are difficult to verify in detail.

Taken together, these Buddhist sutras, Shintō chronicles, commentarial works, and shrine-temple texts form the scriptural tapestry within which Ryōbu Shintō moves. Rather than a single authoritative book, there is a network of writings that mutually interpret one another, allowing practitioners to see the same divine reality shining through both buddhas and kami. In this syncretic vision, scripture is less a fixed boundary and more a set of overlapping mirrors, each reflecting a different facet of a shared sacred world.