Although Buddhism was previously brought to Japan by naturalized people form the Korean Peninsula, the "official" introduction of Buddhism to Japan is dated to 552 in Nihon Shoki otherwise 538 according to the History of Gangōji monastery (元興寺伽藍縁起). A long struggle for power between pro-Buddhism Soga (蘇我) clan and pro -ko’shintō (古神道, ancient Shintō) Mononobe (物部) clan ended with the victory of Soga in 587. Even after Empress Suiko (推古天皇) openly encouraged the acceptance of Buddhism, the ancient belief had not be taken over by Buddhism but has survived for centuries to this day ― It is quite unusual that an indigenous polytheistic belief including nature worship, animism, ancestor worship, shamanism, myth, still prevails in a civilized society like Japan. Rather than discard the old belief system, Buddhists tried to reconcile it by deliberately integrating indigenous belief in their system. They stated that some kami were in fact just local manifestations of universal Buddha to save human beings, and the two entities formed an indivisible whole. This religious theory, honji suijaku (本地垂迹) has characterized ambiguous nature of Japanese religion in which Western people feel uncomfortable.
Hōryū-ji (法隆寺); The temple's pagoda is widely acknowledged to be one of the oldest wooden buildings existing in the world.
The initial period, known as the Asuka period (飛鳥時代; 592 - 710, Asuka jidai) and the Nara period (奈良時代; 710 - 794, Nara jidai) saw the six great Chinese schools, called Nanto Rokushu (南都六宗, lit. Nara six sects) centered around the ancient capitals of Asuka and Nara, where great temples such as the Hōryū-ji (法隆寺) and Tōdai-ji (東大寺) were erected respectively. These were not exclusive schools, and temples were apt to have scholars versed in several of the schools. The Buddhism of these periods was not a practical religion, being more the domain of learned priests whose official function was to pray for the peace and prosperity of the state and imperial house. This kind of Buddhism had little to offer the illiterate and uneducated masses, but became immensely popular among rulers, and it entailed the ascendancy of the Buddhist institutions there and encroaching secular power on state politics.
In 794 emperor Kan’mu (桓武天皇; 737 - 806) moved the capital to Heian-kyō (平安京, modern Kyoto, the imperial capital for the next 1,000 years), after a short-term relocation to Nagaoka-kyō (長岡京) near Kyoto from Heijō-kyō (平城京) in Nare, to diminish the influence of the powerful Nara Buddhist establishments and improve his seat of government geopolitically —while the capital moved, the major Buddhist temples, and their officials, cast behind. Kan’mu also sponsored the travels of the monks Saichō (最澄; 767 - 822) and Kūkai (空海; 774 - 835) to China; they digested Esoteric Buddhism (密教, mikkyo) there, and based on this, founded Japanese Tendai (天台, “Lotus Sutra”) and Shingon (真言, “True Word”) Buddhism respectively.
Enryaku-ji (延暦寺) is a Tendai monastery located on Mount Hiei in Ōtsu, overlooking Kyoto. It was founded during the early Heian period. The temple complex was established by Saichō (767–822), also known as Dengyō Daishi, who introduced the Tendai sect of Mahayana Buddhism to Japan from China.
In the Heian period (平安時代; 794 – 1185, Heian jidai), Tendai flourished under the patronage of the imperial family and nobility, and became the dominant form of mainstream Buddhism in Japan. Saichō reared a temple, Enryakuji (延暦寺) on Mt. Hiei (比叡山) overlooking Kyoto, and it came on a center for the study and practice of the Tendai sect, and incubated most of the influential Japanese Buddhism such as Jōdo shū (浄土宗 "Pure Land"), Jōdo Shinshū (浄土真宗, "True Pure Land School"), Nichiren shū (日蓮宗 “Sun-Lotus”).
kōyasan (高野山) was first settled in 819 by the monk Kūkai, Mt. Kōya is primarily known as the world headquarters of the Kōyasan Shingon sect of Japanese Buddhism. Located in an 800 m high valley amid the eight peaks of the mountain (which was the reason this location was selected, in that the terrain is supposed to resemble a lotus plant), the original monastery has grown into the town of Kōya, featuring a university dedicated to religious studies and 120 temples, many of which offer lodging to pilgrims.
Kūkai brought "Orthodox Esoteric Buddhism" intact with an entire library of tantric materials, huge quantities of Buddhist paintings, and esoteric ritual articles from Tang Dynasty China in 806, and found Shingon school in Japan, and established monastery in Kōyasan (高野山; Mt. Kōya) in 816, that has since become the base and a place of spiritual retreat for Shingon practitioners. Shinto, which lacked its own scriptures and had few prayers, as a result of syncretic practices, widely adopted both Buddhist rituals of Shingon and Tendai.
Kami, Japan’s indigenous religion and foreign Buddhism never quite fused, but a combination of Buddhist and Taoist elements, and the incorporation of shamanistic features of the indigenous religion remained however inextricably linked all the way to the present day.
The Kamakura period saw the introduction of the two religious streams that had perhaps the greatest impact on the country.
Enryakuji, the temple complex of Tendai became a sprawling center of power, attended not only by ascetic monks, but also by brigades warrior monks who fought in the temple's interest.
The official policy of separation of Shintō and Buddhism caused great damage to Buddhism in Japan.
Meiji rulers made Shintō the official religion, creating a form of Shintō known as State Shintō by merging Shrine, Folk, and Imperial Household Shinto.
Young Haruki would often hear his parents discussing eighth-century poetry or medieval war takes at the dinner table. Haruki said, “Throughout my teens I became hate ‘Japanese literature’ and ‘teachers’.”