Confucius was useless. To a disciple inquiring, “May I ask about death?” he’d replied, “You do not even understand life. How can you understand death?”

Growing up in rural Shikoku in the late eighth century, a boy destined for greatness rebelled against being trained for distinguished mediocrity. His name was Kukai. We know him better as Kobo Daishi, a title posthumously bestowed, meaning roughly “great Buddhist sage.” What could Confucianism teach of life if it shrank from facing death? Was death not universal? Kukai sought — demanded — universal, all-encompassing truth. Nothing less would do.

His life (in this world) spanned the years 774 to 835. The Nara Period (710-794) began its end with a sudden, seemingly arbitrary decision in 784 to move the capital from Nara to the as-yet-unbuilt city of Nagaoka. Still, Nara for years to come remained the cultural center. The culture was Chinese. Nara was Chang’an, the Chinese capital, in miniature. China, to Japan, was civilization itself. The Nara Period meant Chinese-style government ruling an imitation Chinese society uncritically steeped in Chinese art, literature, religion and education. The Nara university taught, naturally, Confucianism. Kukai, scion of the minor nobility, attended. It was the path to a career in the civil service.

He dropped out. He was no civil servant, and no Confucian. Better a truth-seeking beggar than a self-satisfied bureaucrat.

Kukai left Nara and wandered alone through the mountains of his native Shikoku. A Buddhist monk taught him a mantra invoking Akasagarbha, the supreme deity of the universe. The invocation could not occur just anywhere. It required a certain setting. Where? There was no telling. He’d wander. When he saw it, he’d know.

A cave in what is now Kochi Prefecture offered lucky refuge from a storm. “One morning,” he wrote years later, “I was meditating in the cave at Cape Muroto, when the morning star … flew into my mouth and I saw before my eyes a figure of Akasagarbha enveloped in his halo.”

The modern mind, differently furnished, recoils, bewildered — but the experience, whatever it may have involved, made Kukai what he has been to Japan down the centuries. A walking pilgrimage around Shikoku, centuries old, its 1,200-kilometer route punctuated by 88 temples, testifies to his enduring significance.

“The pilgrim believes that he walks with the Daishi at his side,” wrote Oliver Statler in “Japanese Pilgrimage” (1983). “Some say that though Kobo Daishi left this life, he did not die, that he lies uncorrupted in (his tomb on Mount Koya) under these ancient trees, awaiting the coming of the future Buddha who will signal the salvation of the world.” That was to be in some 5 million years — but what is time? A mere eyeblink measured against immeasurable eternity.

From a purely human standpoint, Buddhism can seem bleakly remote. Salvation is possible, but few qualify. It requires vast learning, strict austerity, superhuman self-mastery, untold numbers of births and deaths. The saint rises to the challenge; the ordinary man sinks into despair at the mere thought of it. Women face the additional hurdle that nirvana is closed to them, barring rebirth as men.

That can’t be right, thought Kukai. An obscure sutra encountered in his early wanderings — originating in India, translated in China, existing in Japan only in fragments — pointed the way to what came to be called “esoteric Buddhism.” The seeds of Buddhahood are in everyone, it taught — men and women, rich and poor, learned and unlearned. An intriguing suggestion — which could hardly be followed up in Japan, however. Japan’s Buddhist roots were too shallow, going back a mere two centuries. The true masters, the great teachers, the voluminous texts, were in China. For 200 years primitive Japanese boats had been plying the stormy seas separating the two countries, carrying monks and merchants more eager to study and trade than they were fearful for their lives. It was a chancy business, that crossing — as likely to end fatally as not.

In 804 Kukai went to China.

“How can we describe that miracle in the history of our planet, the prosperity of Chang’an?” mused historical novelist Ryotaro Shiba (1923-96) in “Kukai the Universal: Scenes from His Life.” The miseries and perils of the month-long crossing must have heightened its splendor in Kukai’s eyes. It was the greatest city on Earth — population 1 million.

Nara, itself vast by the standards of the time, had 200,000 people but none of Chang’an’s cosmopolitanism. All ninth-century roads led to Chang’an, drawing Buddhists, Confucians, Christians, Muslims, Jews, Zoroastrians — was any major religion in the world unrepresented? As with sages and students, so with merchants and buyers. “It was interesting (to Kukai),” writes Shiba, “to see how a caravan that had been traveling all the way from lands unknown to him removed the bundles from the camels’ backs. Another attraction was an open-air show of Persian girls dancing.” Other monks may have shut their eyes to them. Not Kukai. He shut his eyes to nothing. Sex too was “universal.” Preserving his priestly celibacy, he made libido a vehicle to truth.

He spent two years in Chang’an. Many other students spent 30; he was quicker than they. He mastered his texts — and the Sanskrit language to boot — with astonishing speed and thoroughness, urged homeward, says Shiba, by “his self-imposed mission to propagate his religion” in Japan.

The seeds of Buddhahood are in all of us — such was Kukai’s ultimate message. Kukai was Japan’s first spokesman for “all of us” — ordinary people as opposed to the chosen few. He taught humankind that the supreme element in Buddhism is (in Shiba’s words) “breathing in accordance to the breathing of the universe.” The Shingon (True Word) Buddhism he brought back from China emphasizes ritual over study, mudra (spiritually significant hand gestures) over reason, mantra (mystic utterances) over discourse.

Zen students will see in this a proto-Zen. Pure Land Buddhism, whose faithful call on Amida Buddha for rebirth in the jeweled “Western Paradise,” is no less a Shingon offshoot. Pilgrims, as they walk, pray to Kukai for miracles — the infertile for children, the drought-stricken for rain, the ill for health. No one in all Japanese history has ever inspired such faith as has, and does, Kobo Daishi, sleeping in his tomb, the morning star in his mouth.

Michael Hoffman’s book “In the Land of the Kami: A Journey into the Hearts of Japan” is currently on sale.