In Ryōbu Shinto, Buddhism plays a significant role in the syncretic mix of Shinto and Buddhism. This unique form of Shinto emerged in Japan during the Heian period (794-1185) and was heavily influenced by the arrival of Buddhism from China and Korea.

One of the main aspects of Ryōbu Shinto is the belief in the two realms of existence - the physical and spiritual realms. This concept is derived from the Buddhist belief in the two truths, the ultimate truth and the conventional truth. In Ryōbu Shinto, the physical realm is represented by Shinto deities, known as kami, while the spiritual realm is represented by Buddhist deities, known as buddhas. This blending of the two realms is a key feature of Ryōbu Shinto and is known as honji suijaku, which means "original ground and manifested traces."

Furthermore, Ryōbu Shinto incorporates many Buddhist rituals and practices into its worship. For example, the purification ritual of misogi, which involves purifying the body and mind through water, is derived from Buddhist purification practices. In addition, the use of incense, chanting, and meditation are also common in Ryōbu Shinto ceremonies, all of which have their roots in Buddhism.

Buddhism also plays a role in the mythology and cosmology of Ryōbu Shinto. The Buddhist concept of the cycle of death and rebirth, known as samsara, is intertwined with the Shinto belief in the cycle of life and death. This is reflected in the story of the sun goddess Amaterasu, who is said to have descended to the underworld and returned to the world of the living, symbolizing the cycle of death and rebirth.

Moreover, many Buddhist deities are also worshipped as kami in Ryōbu Shinto. For example, Kannon, the Buddhist goddess of mercy, is revered as a kami in Shinto shrines. This blending of deities further highlights the syncretic nature of Ryōbu Shinto.

In conclusion, Buddhism plays a crucial role in Ryōbu Shinto, shaping its beliefs, rituals, and mythology. The syncretic mix of Shinto and Buddhism in Ryōbu Shinto has created a unique and harmonious religious tradition that continues to be practiced in Japan today.