Buddhism was introduced in Japan and concretely established in the Kingdom named ‘Nara’ [奈良] approximately in the 12th Century CE until Meiji [明治] era in 2,455 BCE. However, Buddhism always had been under patronage and embrace of the ruling and elite class of the societies. Sometimes it was politically steered and intentionally manipulated to fit best with their situation and environment, or to best serve social and political aspects.
It is believed that several major doctrines were introduced in Japan in early period, including Sarvāstivāda (Skt.: Pālī, sabbatthivāda) – one of the important school of Indian Buddhism that separated from the main body of the Elders (Straviras) around the mid-3rd century BCE, literally means ‘the school that holds that everything exists’, Sautrātika (Skt.) – an early school whose origins and tenets are obscure. Vasumitra mentions a school called the Samkrāntikas, ascribing to it specific teachings concerning rebirth and no other teachings. The Madhayamaka (Skt.) also was introduced in Japan along with those major doctrines. Its name literally means ‘The middle school’. This Buddhist philosophy is believed to be found by a prominent Buddhist figure and thinker named ‘Nāgārjuna’ in the 2nd century CE. Later, this tenet was extremely influential within the Mahāyana tradition. Its followers mainly are called as ‘Mādhayamika’. The rest ones should have been aware of Yogācāra School of ‘Asaŋga Vasubandhu’, ‘Tantra’ School; ‘Sukhāvati’ literally means ‘the realm of bliss’, and ‘Zen’ [Skt. D᷂hayāna, Pālī Jhāna].
However, along with their establishment in Japanese society, those doctrines also gradually encountered transformation. It is believed that many of those Schools were found and originated from pure philosophical emphasis of Buddhism in early period. Nonetheless, most of them later were altered and adjusted to serve as Japanese academic constituents. On the one hand, of those Schools whose preliminary core teaching based upon faith and piety were then adjusted to fit and combine with conventional Japanese faith and customs. However, from then, the adaptive doctrines have been prosperous in Japan for millenniums until the current time.
It is significant to observe religious situation in Japan. Interestingly through systematic observation, it indicates that the main religion is ‘Shinto’ [神道]. It is believed that this indigenous religion of Japan is not much an organized, unified religion as a cultural complex of religious myths and rituals carried out originally by clan and village groups and centering on tutelary deities called ‘Kami’ [神]. These ‘Kami’ can be considered deities with names and stories attached to them, as the case of the sun goddess Amaterasu [天照大神・天照大御神（あまてらすおおみかみ ]; as personifications of forces of nature; or as the spirit of natural features like waterfalls, stones, trees and mountains etc. What should be observed here is that Japanese belief mainly is a combination of ‘Shinto’ and ‘Buddhism’ which fits best with Japanese personality – it can be realized as a master piece of invention. ‘Shinto’ reflects earnestness, enthusiasm and ambition embedded in traditional Japanese uniqueness in character, whereas ‘Mahayana’ Buddhist doctrine reflects the image of compassion, kindness and sustenance.
Nonetheless, Buddhism in Japan has been through several forms of adaptation and transformation over several stages since it was established. Data shows significant figures reflect remarkable information regarding religious situation in Japan. In 2,503 BCE, observation indicates that 9.2 million Japanese are ‘Zen’ followers, 8.5 millions are those of ‘Sukhavati’ doctrine, and 2.5 million belong to the ‘Nichiren’ [日蓮]. Three decades later the observation had been done in the same manner. However, statistic indicates significant alteration in numbers of doctrinal piety. It appears that ‘Zen’ members had increased and reached 18 million whereas the followers of ‘Sukhavati – the realm of bliss’ reached 39 million. It is believed that ‘Nijiren’s members had increased outnumbered by 65 million. Apparently Japan’s population in the year of observation was much lower by numbers. Therefore, it indicates that each Japanese hold more than one faith at one time. It is claimed that the followers of ‘Shinto’ at the same time are devoting Buddhist, or perhaps, ‘Zen’ and ‘Nijiren’.
Thus, currently the population of Japan is 126, 771,662 , however statistic shows a ‘cross religion or faith’ phenomenon in which the numbers of followers of both major religions are outnumbered actual figures by 193, 797,630. This ‘cross faith’ phenomenon indicates that Japanese adopt and embrace more than faiths at the same time.