Within the Ryōbu Shintō synthesis, the Mahāvairocana Sūtra (Dainichi-kyō) stands at the very heart of the system. This esoteric scripture, central to Shingon, provides the doctrinal basis for understanding the great cosmic Buddha Mahāvairocana (Dainichi Nyorai) as the ultimate ground of reality, and it is through this lens that major kami, especially the solar deity, are interpreted. The text’s vision of an all-pervading Buddha allows the kami to be seen not as separate rivals, but as expressions of a single, luminous source. In this way, Ryōbu Shintō uses the Dainichi-kyō to bridge the apparent divide between indigenous deities and Buddhist cosmology, treating them as two sides of one sacred coin.

Alongside this, the Vajraśekhara Sūtra (Kongōchō-kyō) serves as a second pillar of the tradition. Together with the Mahāvairocana Sūtra, it undergirds the dual-mandala structure that became emblematic of esoteric Buddhism and, by extension, of Ryōbu Shintō’s “two-fold” vision. The mandalic arrangements and deity-assemblies of this sutra are mapped onto shrine spaces, ritual patterns, and the ordering of kami, allowing the architecture of Buddhist enlightenment to be read into the landscape of Shintō worship. Through this pairing, the esoteric “diamond” and “womb” realms are not merely abstract cosmological schemes, but living templates for understanding the presence of the divine in Japan.

Beyond these core esoteric texts, other sutras play important supporting roles in shaping Ryōbu Shintō thought. The Lotus Sūtra (Hokke-kyō) is particularly significant, as it nourishes the honji suijaku paradigm in which buddhas and bodhisattvas are regarded as the original ground (honji) and the kami as their local manifestations (suijaku). This same sutra, especially its Universal Gate chapter, also provides a scriptural basis for linking compassionate kami with Avalokiteśvara (Kannon), further tightening the web of correspondences between the two traditions. The Nirvāṇa Sūtra contributes its teaching on Buddha-nature, which is extended to encompass not only human beings but also the kami and the land itself, suggesting a world suffused with latent awakening.

Within this broader constellation, additional texts deepen and refine the integration. The Heart Sutra (Hannya Shingyō) is drawn upon for its concise articulation of emptiness and wisdom, concepts that subtly inform how the fluid identities of kami and buddhas are understood. The Golden Light Sutra (Konkōmyō Saishōō-kyō) is employed in relation to protection of the realm, resonating with long-standing concerns for the welfare of the state and its deities. In some contexts, Pure Land sutras concerning Amitābha and the Pure Land are also harmonized with shrine cults, allowing specific kami or sacred sites to be read through the imagery of Pure Lands. Taken together, these sutras do not form a separate canon, but rather a woven tapestry through which Shintō ritual life is reinterpreted in the light of esoteric Buddhist metaphysics.