In 593, Prince Hachiko arrived in Dewa province as a fugitive. His father, Emperor Sushun -- the 32nd emperor of Japan -- had been assassinated by the powerful Soga clan. Rather than rally an army or seek vengeance, the prince vanished into the mountains and devoted himself to spiritual discipline. Through punishing ascetic exercises and extended periods of penance, he came to worship Haguro Gongen, the deity of Mount Haguro. His practice expanded to Mount Gassan and Mount Yudono, and he eventually enshrined all three deities at a temple on Mount Haguro's summit. What began as one man's refuge became a magnet for pilgrims. Over the following centuries, devotees trekked thousands of miles to reach these shrines during summer, when the higher peaks shed their snow. Among them came En no Gyoja, the founder of Shugendo, and Kukai, who would establish Shingon Buddhism -- two of the most influential figures in Japanese religious history.

Each mountain carries its own spiritual weight. Mount Haguro, at 414 meters the smallest, is the most accessible and the only peak open year-round. It houses the primary Dewa Shrine at its summit, where the Sanzan Gosaiden venerates all three mountain deities under one roof. The approach passes a 600-year-old five-story pagoda designated as a National Treasure of Japan, then ascends 2,446 stone steps through ancient cedar forest. Mount Gassan towers above at 1,984 meters, the tallest of the trio and the second-highest point in the Shonai region. Its upper slopes host rare alpine plants and marsh vegetation, and its simple summit shrine offers Shinto purification to arriving pilgrims. Heavy snow keeps it sealed from late autumn through spring. Mount Yudono, regarded as the spiritual heart of the three, is the most sacred. Its shrine possesses a goshintai -- an object believed to be directly connected to a deity -- and the entire precinct is considered so holy that photography remains prohibited and pilgrims are sworn to secrecy about what they witness inside.

The Japanese practice of associating religious belief with sacred mountains has a name: sangaku shinko. It permeates the country's spiritual landscape so deeply that virtually every prominent peak has hosted a shrine at some point. The Dewa Sanzan sit at the pinnacle of this tradition, sacred to Shinto, Buddhism, and especially Shugendo -- a syncretic discipline that blends elements of both with Taoist-influenced mountain asceticism. Shugendo practitioners, called yamabushi, undergo rigorous physical and spiritual training on these peaks. Mount Haguro serves as the entryway; Mount Gassan and Mount Yudono represent progressively deeper stages of the spiritual journey. The yamabushi wear distinctive white robes and blow conch shells as they traverse the trails, following paths established more than a millennium ago. Their practice is not historical reenactment -- it is living religion, with laymen taking part in the same ascetic disciplines each summer.

The Meiji Restoration of 1868 nearly severed Shugendo at the root. When the new government dissolved the centuries-old amalgamation of Shinto and Buddhism and elevated Shinto as the state religion, Shugendo -- which drew from both traditions and more -- found itself without official standing. Many Shugendo priests abandoned their vows and returned to secular life. The shrines of Dewa Sanzan were reclassified: Hagurosan Shrine and Yudonosan Shrine became kokuhei shosha, government-supported Shinto shrines, while Gassan Shrine received the higher designation of kanpei taisha. The underlying mountain worship continued among the faithful, but its institutional structure was badly damaged. Recovery came slowly. After World War II, religious freedom was restored, and Shugendo was permitted to reorganize as a minor religious group. The three shrines were eventually reclassified as equal Beppyo shrines. Today, the annual cycle of pilgrimage continues: the mountains open each summer with festivals, the yamabushi ascend, and the shrines close again when the snow returns.