A name every child in Japan knows
空海 Kūkai means "sky and sea." He was born in 774 in the province of Sanuki on Shikoku and, according to tradition, entered eternal meditation on Kōyasan in 835. In Japan practically everyone knows him by his posthumous title 弘法大師 Kōbō Daishi, "the Great Master who spread the Dharma."
More than 1,200 years later, tens of thousands of pilgrims still follow the 88 temples of Shikoku every year in his footsteps. On Kōyasan they visit his mausoleum in Okunoin, where, according to the faith of many Japanese, he hasn't died but is meditating and waiting. Who was this man?
From the academy into the mountains
Kūkai came from the Saeki family, a respected local family in Sanuki. At eighteen he entered the state academy (daigaku) in the capital, which prepared young men from good families for a career as officials, with Confucian classics and Chinese literature.
Kūkai broke off this path. In 797, at the age of twenty-four, he wrote the Sangō shiiki, "Indications of the Goals of the Three Teachings," in which he compared Confucianism, Daoism and Buddhism in the form of a story and concluded that Buddhism goes deepest. What drove him was a question that never let go of him: how can a person reach awakening, not in a distant future life, but in this body and in this life?
Mountain asceticism and the morning star
Instead of becoming an official, Kūkai went into the mountains and practiced like the mountain ascetics of his time, the forerunners of what would later be called Shugendō. In this period he practiced the Gumonji-hō, the ritual centered on the mantra of Kokūzō Bosatsu. In the Sangō shiiki he writes that he practiced in the mountains of Awa and at Cape Muroto in Tosa, and that the morning star came toward him. Later legend says that it flew into his mouth.
A popular explanation connects his name with the cave at Cape Muroto, from which you see nothing but sky and sea. Whether he really chose his name there can't be proven, but the image fits very well.
China and the transmission from Huiguo
In 804 Kūkai traveled to Tang China with a Japanese embassy. He was supposed to stay for twenty years. It turned out to be two.
In the capital Chang'an he met the master Huiguo at the Qinglong temple, the seventh patriarch of esoteric Buddhism. In his report to the emperor, Kūkai writes that Huiguo greeted him with a smile and said that he had known Kūkai would come and had been waiting for him for a long time. Within a few months Huiguo gave him the complete transmission, the initiations into both mandalas, the Womb Realm (Taizōkai) and the Diamond Realm (Kongōkai), together with the rituals, mantras and Siddham (Bonji in Japanese). Kūkai received the initiation name Henjō Kongō 遍照金剛, "the diamond that illuminates everywhere," which is a name of Dainichi Nyorai.
At the end of 805 Huiguo died. Forty years later, the great persecution of Buddhism in China under Emperor Wuzong severely weakened esoteric Buddhism there, so what Kūkai had brought to Japan soon existed in this completeness almost only in Japan.
The lineage of the Shingon patriarchs runs Dainichi Nyorai, Kongōsatta (Vajrasattva), Nāgārjuna, Nāgabodhi, Vajrabodhi, Amoghavajra, Huiguo and Kūkai, who is counted as the eighth patriarch.
Founding a tradition
In 806 Kūkai returned to Japan with a large number of texts, ritual implements and mandalas.

-
774Born on Shikoku in the province of Sanuki, into the Saeki family
-
791Enters the state academy in the capital at eighteen
-
797Sangō shiiki, comparing Confucianism, Daoism and Buddhism; years of mountain practice and the Gumonji-hō
-
804Departure to China with the embassy to the Tang court
-
805Transmission from Huiguo at the Qinglong temple in Chang'an, both mandalas
-
806Return to Japan with texts, mandalas and ritual implements
-
816Permission to found Kōyasan in the mountains of the Kii Peninsula, still the main seat of Shingon
-
823Receives Tō-ji in Kyoto from the emperor
-
835Enters eternal meditation (nyūjō) on Kōyasan
With Kōyasan he created a place for meditation and ritual far away from the capital, which over the centuries grew into a whole temple town. With Tō-ji he had a center in the capital Kyoto.
Kūkai was more than the founder of a school. He's counted among the three great calligraphers of his time (sanpitsu), he wrote a great many works, and in 828 he founded the Shugei Shuchiin, a school that was also open to people who weren't from the nobility.
Sokushin jōbutsu 即身成仏
Kūkai's central message is in the title of one of his main works, Sokushin jōbutsu gi, "The Meaning of Becoming a Buddha in This Very Body." His answer to the question that had driven him since his youth was yes, awakening is possible in this life and in this body. The way to it is the three mysteries (sanmitsu 三密) of body, speech and mind, that is, mudra, mantra and contemplation, through which the practitioner comes into resonance with the Buddha. The foundation is Dainichi Nyorai, the cosmic Buddha, whose body is the whole universe. Put simply, a person doesn't have to become something he isn't already. He has to recognize it.
In another work, Shōji jissō gi, "The Meaning of Sound, Word and Reality," Kūkai writes a famous verse: "The five great elements all have resonance, the ten realms all possess language, the six kinds of sense objects are all letters, and the Dharmakāya is reality." For Kūkai, the whole world speaks, and the Siddham characters are a key to it. The Siddham A stands for the "originally unborn," the origin of everything, and the contemplation of this syllable, Ajikan, became one of the central meditations of Shingon.
Kūkai and Shingon Reiki
Much of what I work with in Shingon Reiki comes from the world Kūkai brought to Japan, the Siddham, the three mysteries and the meditations with the Buddhas and bodhisattvas. The second Reiki symbol, Sei He Ki, for example, goes back to the Siddham syllable hrīḥ. At the same time, Shingon is only one of the roots that Usui drew on, alongside Shugendō, Shintō and shamanic Daoism.
The man who never stopped meditating
In the third month of 835 Kūkai entered eternal meditation on Kōyasan, nyūjō. According to tradition, he waits there for Miroku Bosatsu, Maitreya, the Buddha of the future, who is said to appear in 5.67 billion years. In 921 the court awarded him the title Kōbō Daishi. To this day, monks prepare a meal for him twice a day and carry it in procession to the mausoleum in Okunoin. For many Japanese, Kūkai isn't a historical figure but a living presence.
I experienced this myself on the Shikoku pilgrimage. My first attempt ended after about ten days at temple 24, and a year later I walked all 88 temples on foot. Pilgrims on Shikoku traditionally wear a hat with the words dōgyō ninin 同行二人, "two traveling together." The second one is Kūkai, and the pilgrim's staff stands for him. Have you ever walked a pilgrimage route yourself?

Experience Kūkai's Tradition
Much of what Kūkai brought to Japan, the Siddham and the Three Mysteries, lives on in Shingon Reiki. The path begins with Level 1.