Kūkai (空海; 27 July 774 – 22 April 835[1]), born Saeki no Mao (佐伯 眞魚),[2] posthumously called Kōbō Daishi (弘法大師, "The Grand Master who Propagated the Dharma"), was a Japanese Buddhist monk, calligrapher, and poet who founded the esoteric Shingon school of Buddhism.

[3] Shingon followers usually refer to Kūkai by the honorific title of Odaishi-sama (お大師様, "The Grand Master"), and the religious name of Henjō Kongō (遍照金剛, "Vajra Shining in All Directions").

Kūkai was born in a period of important political changes with Emperor Kanmu (r. 781–806) seeking to consolidate his power and to extend his realm, taking measures which included moving the capital of Japan from Nara ultimately to Heian (modern-day Kyoto).

[5] The family fortunes had fallen by 791 when Kūkai journeyed to Nara, the capital at the time, to study at the government university, the Daigakuryō (大学寮).

Around the age of 22, Kūkai was introduced to Buddhist practice involving chanting the mantra of Kokūzō (Sanskrit: Ākāśagarbha), the bodhisattva of the void.

At age 24 he published his first major literary work, Sangō Shiiki, in which he quotes from an extensive list of sources, including the classics of Confucianism, Daoism, and Buddhism.

During this period in Japanese history, the central government closely regulated Buddhism through the Sōgō (僧綱, Office of Priestly Affairs) and enforced its policies, based on the ritsuryō legal code.

Ryuichi Abe suggests that the Mahavairocana Tantra bridged the gap between his interest in the practice of religious exercises and the doctrinal knowledge acquired through his studies.

Scholars are unsure why Kūkai was selected to take part in an official mission to China, given his background as a private monk who was not sponsored by the state.

After further delays, the Tang court granted Kūkai a place in Ximing Temple, where his study of Chinese Buddhism began in earnest.

It was in 805 that Kūkai finally met the monk Huiguo (746–805) the man who would initiate him into Chinese Esoteric Buddhism (Tangmi) at Chang'an's Qinglong Monastery (青龍寺).

Huiguo came from an illustrious lineage of Buddhist masters, famed especially for translating Sanskrit texts into Chinese, including the Mahavairocana Tantra.

Kūkai describes their first meeting: Accompanied by Jiming, Tansheng, and several other Dharma masters from the Ximing monastery, I went to visit him [Huiguo] and was granted an audience.

Whereas Kūkai had expected to spend 20 years studying in China, in a few short months he was to receive the final initiation, and become a master of the esoteric lineage.

[6] Huiguo died shortly afterwards, but not before instructing Kūkai to return to Japan and spread the esoteric teachings there, assuring him that other disciples would carry on his work in China.

Kūkai's return from China was eclipsed by Saichō, the founder of the Tendai school, who found favor with the court during this time.

Kūkai petitioned the Emperor to allow him to carry out certain esoteric rituals which were said to "enable a king to vanquish the seven calamities, to maintain the four seasons in harmony, to protect the nation and family, and to give comfort to himself and others".

With the public initiation ceremonies for Saichō and others at Takao-san temple in 812, Kūkai became the acknowledged master of esoteric Buddhism in Japan.

Meanwhile, Kukai's new esoteric teachings and literature drew scrutiny from a noted scholar-monk of the time named Tokuitsu, who traded letters back and forth in 815 asking for clarification.

The dialogue between them proved constructive and helped to give Kūkai more credibility, while the Nara Schools took greater interest in esoteric practice.

Saga gave Kūkai free rein, enabling him to make Tō-ji the first Esoteric Buddhist centre in Kyoto, and also giving him a base much closer to the court, and its power.

In response to a request from the emperor, Kūkai, along with other Japanese Buddhist leaders, submitted a document which set out the beliefs, practices and important texts of his form of Buddhism.

In his imperial decree granting approval of Kūkai's outline of esoteric Buddhism, Junna uses the term Shingon-shū (真言宗, Mantra Sect) for the first time.

An imperial decree gave Kūkai exclusive use of Tō-ji for the Shingon School, which set a new precedent in an environment where previously temples had been open to all forms of Buddhism.

This was the final step in establishing Shingon as an independent Buddhist movement, with a solid institutional basis with state authorization.

The school closed ten years after Kūkai's death, when it was sold in order to purchase some rice fields for supporting monastic affairs.

"[12] Legend has it that Kūkai has not died, but entered into an eternal samadhi (meditative trance) and is still alive on Mount Kōya, awaiting the appearance of Maitreya, the Buddha of the future.

It is called the Hōgō (treasure name) and is:[15] namu daishi henjō kongō 南 無 大 師 遍 照 金 剛The mantra means "homage (namu) great teacher (daishi) henjō kongō (Vairocana vajra, Kūkai's secret tantric name).

When searching for a place on Mount Kōya to build a temple, Kūkai was said to have been welcomed by two Shinto deities of the mountain—the male Kariba, and the female Niu.

Later, both Kariba and Niu were interpreted as manifestations of the Buddha Vairocana, the central figure in Shingon Buddhism and subject of Kūkai's lifelong interest.