I later meet Daizaburo Sakamoto, a manga illustrator turned professional Yamabushi. With his man bun, MacBook and loose linens, he looks like the ultimate hipster - an impression that only intensifies when I learn that he made his backpack out of animal hide and forges his own steel knives from iron-ore dust. Daizaburo moved here from Tokyo and began gathering mountain survival techniques into material for a best-selling book. "Human life used to be indistinguishable from nature," he tells me, "but today it has become so developed that we don't need nature to survive. The perception of culture in cities is spread so thin that you can barely feel it, whereas in the mountain it has evolved vertically - it's deep-rooted. When we reconnect with these ancient cultures, we can rediscover who we are."

With these words ringing in my ears we make our way to the former temple of Saikan on Mount Haguro, where all three mountain deities are enshrined and where our training will take place. Arriving by night I can just make out the shadowy outlines of mighty trees and the triangular peaks of temples, and the next morning when I slide back my room's screen door I'm greeted by huge, reddish-brown trunks crawling with greenery and the sun streaming through the branches in a scene that feels almost computer-generated.

We drive to Daishobo, another pilgrim lodge and the home of Master Hoshino, the sendatsu (mountain master) who will lead us through our training. The only word permitted to be spoken is "uketamo", which translates as "I humbly accept with an open heart", so before silence descends we receive our shiroshozoku. These are the white garments worn by the dead, as in order to be reborn we must first die. We're also given a paper necklace called a shime, which just like the ropes across the torii gates that mark an entrance into divine ground, signifies that we are temporarily becoming sacred. The Master and his assistant wear colossal conch shells strung around their necks which they blow regularly to ward off evil spirits and call us to action. As it sounds for the first time Master Hoshino enters the room and we bow and chant in front of a shrine before lining up and marching to Mount Kinbo.

Cut to me standing in front of the waterfall, where unfortunately it seems there's a ladies-first policy. Master Hoshino beckons and I nervously wobble over the rocks on my dodgy ankle and duck under the ice-cold stream. We've been given a shortened version of a heart sutra (prayer) to recite, but as soon as the water hits my mind goes blank and it's all I can do to stop myself from squawking and flapping like the drenched goose I must resemble. Emerging a few moments later, however, I feel strangely refreshed, and Master Hoshino later tells me that it's here he feels a shift in me from fear to acceptance.

After a quick break back at the lodge - in which I'm told no for reading as it takes me out of the present moment - we follow up a session of meditation with a night walk. Fortunately it's a full moon and the way is bright, but I still can't help stabbing the stone- studded ground with my walking stick and frantically waving my lantern. The Master walks ahead, his ghostly form shimmering dustily in the darkness, until we reach a bridge from which we can hear the river roar and fireflies blink on and off. It's a lesson in trusting your senses and from this point on I give in more readily to the path, the meditative pace of putting one foot in front of the other lulling me into a state of peace.

Returning to the lodge we cram into a small room for a smoke meditation, meant to symbolise passing through the world of hell. I'm sworn to keep the details secret, but suffice to say that my head is reeling when I emerge and am told to go to bed, but to be prepared to leave on the second sounding of the conch. When it blares an inestimable number of hours later, I stagger to my feet and into a fierce downpour to tackle Mount Haguro's ancient pilgrimage route, Ishi-Dan.

The next few hours pass in a blur of sodden splendour as we make our way up the 2,446 stone steps cut into the side of the mountain. Gargantuan cedar trees and bushes dotted with milky-blue hydrangeas fringe the path, while slabs hewn with runes hide among them. We stop to chant sutras at various shrines and temples, most notably the 600-year-old, five-storey Go-Jyu-No-Toh pagoda, where I look up and see sheets of raindrops bouncing off the edges of its roofs as if I'm in a video-game cutscene. We pass a 1,000-year-old redwood known as the "Grandpa Tree" which has a tasselled shime tied around its trunk as a reminder of the longevity of the natural world. Finally we reach the network of shrines at the top of the path and enter the largest, Sanjin Gosaiden, for another round of worship and a ceremony that concludes with us drinking a bowl of sake. I'm spared the journey down due to my injury and after waiting for the rest of our group to navigate the steep route back, we return to the lodge for our "graduation".

After a much-needed shower - washing is prohibited throughout the training in order to put participants in a more animalistic state - we sit down for a celebration brunch of shojin ryori cuisine and I'm finally able to chat to Master Hoshino. "The training is about learning from nature and the gods around us, just as those in ancient times did," he tells me. "We used to learn everything from nature and therefore our ability to sense was highly developed, whereas today we are taught to 'think' rather than 'feel'. As a result, we all tend to think and see the world the same way. I know that 'mindfulness' has become a popular term in the West, but it's the wrong way of looking at things - we need to 'feel' first and contemplate later. Being reborn on the mountain is about getting back to our original state when we're born, before we lose our ability to sense."

Before we leave Master Hoshino takes us to the ocean for a final meditation, although the waves stirred up by the previous day's downpour are a little too savage for true reflection. As I'm slapped repeatedly in the face by spray and swallow lungfuls of salty water, I spot Master Hoshino gleefully bobbing up and down, laughing, before he disappears off into the distance. Clambering up to a nearby lighthouse, I sit and gaze across the sea back towards the West. It would be wrong to say that I feel like a different person entirely, but I do feel a certain sense of calm, trust in my intuition and acceptance that I definitely didn't possess before. "Uketamo," I think, as I stare across the water, towards home.

This article appears in Volume 24: The Slow Issue.

"HUARGH HUARGH" As our motley band of pilgrims thrusts our arms back and forth in unison in a move more naturally associated with drunk dads at weddings, I have what can only be described as a momentary out-of-body experience. I'm balanced on a rock in the middle of the Japanese forest, the lone woman surrounded by men dressed in nothing but loincloths. In front me is our leader, a tiny force of nature topped with a moon-white beard, while the man we've nicknamed "the Spartan" - a six-foot-six, tattooed CrossFit trainer - towers over me to my left. Our chants ring into the trees as we prepare to step under a waterfall and purify ourselves, the first stage in our quest to be reborn.

It's a spectacularly weird moment, and one that only makes sense in the context of the previous few days of mental, physical and spiritual preparation in the northern region of Shōnai. A far cry from the Western world's readiest notions of Japan - all neon-saturated cities, bullet trains and robot waiters, perhaps punctuated with the odd cherry blossom-shrouded temple - this rural province is known for both farming and the ongoing practice of Shugendō, an ancient form of folk religion centred on the three sacred mountains of the Dewa Sanzan. A hybrid of Zen and Esoteric Buddhism, Shintoism and nature worship, Shugendō emphasises immersion in nature as the pathway to enlightenment. Its mountain priests, the Yamabushi, embark on extended periods of pilgrimage which often involve incredible feats of endurance, such as traversing perilous terrain, meditating in enclosed spaces filled with acrid smoke, leaping over fire and, in times gone by, even self-mummification.

I'm here because for the first time in its 1,300-year history Shugendō is becoming available to non-Japanese speakers, who perhaps hope to find some sort of truth of their own and an antidote to the artificiality of modern living. Arriving fogged with jet lag and having sprained my ankle the week before, I'm relieved that my experience begins at sea level - the Yamabushi believe that all life trickles down from the mountains before we ascend to their peaks in the afterlife and then join with the essential nature of the universe, so my journey is to take the same shape of ocean, mountain, ocean.

Zipping along Shōnai's roads I gaze out over a vast, flat expanse of swaying rice paddies, the light bouncing o the waterlogged rows of seedlings like silk stretched tight on the loom or stitched-together spiderwebs. Tsuruoka City in Shōnai is the only place in Japan to have been awarded the status of Unesco Creative City of Gastronomy, an achievement made possible by the region's rare topography as a broad and windy plain surrounded by a plentiful supply of fresh water from the mountains.

Our destination is Naa, a family-run farmstay and restaurant recently voted the best in Japan. Strolling through patches of aubergine, chestnut and watermelon, the restaurant manager, Norimasa Onodera, tells me how after the Second World War farmers were encouraged to use pesticides and so today less than 0.5 per cent of all farming in Japan is organic. His father, Kisaku, made the pioneering decision to return to organic farming over 40 years ago and now both father and son are dedicated to convincing others to do the same. "The soil is like a person - it needs to be fed the right things in order to thrive," Nori explains. Having only picked up a knife five years ago, he tells me, "What I learned from my mother and my knowledge of the vegetables we grow are my only weapons. Every family should pass down this knowledge - it forges a connection to the land". All the vegetables he serves in the restaurant are produced here and anything else is sourced locally. I feast on leaves blanched in boiling water and dipped in a tangy, mustard-like sauce, sweet aubergine in miso paste and, of course, bowls of sticky rice from the family paddies.

A similar tale emerges at Chikeiken, founded by 69-year-old Mitsu Chonan. Born into a farming family, at the age of 23 her mother fell seriously ill and she was entrusted with caring for her in addition to working on the farm and raising her young family. My jaw drops when I hear that the beautiful calligraphy, ceramics and tapestries that decorate the walls are her own. When I ask how on earth she managed to develop these skills in addition to running a home and business, she laughs, "The gods give everyone 24 hours in a day... I only focus on the present moment and what I can do. I couldn't travel but I wanted to experience the world, so I opened the restaurant to bring the world to me."

As we tuck into shards of bamboo shoots festooned with tiny sardines, shiny slices of mackerel balanced atop golden root vegetables and miniature clusters of mushrooms, Mitsu tells me how she believes we should eat seasonally and locally to maintain our health. "Globalisation means that we are losing the idea of local flavours. I don't use medicine - I eat what I grow on the farm and forage from the mountains, whether that's bitter spring herbs to detox or cool summer melon to regulate body temperature." I smile as I think about how this powerhouse grandmother has been quietly practising terms like farm-to-table and foraging long before they became foodie buzzwords Mitsu's attitude of squeezing the marrow out of each moment starts to make sense at the Zenpo Temple. We wash our hands and mouth before passing several pagodas and walking up the steep steps to the main temple, a peaceful network of shaded corridors and rooms for worship and meditation. Zen Buddhism is a compacted version of the teachings of the Buddha that emphasises the now, the here and the self, with Shugendō allowing us to concentrate on these three things. Seated meditation, or zazen, is a core part of familiarising ourselves with the state of emptiness that we came from and to which we will return, so we settle on to the straw-matted floor in as close to lotus position as we can manage. I struggle with the concept of stillness but am told that the aim isn't to clear your mind entirely, but rather to observe your thoughts and let them go. It's a task my iPhone-addled brain can't quite grasp, yet provides a vital understanding of the intuitively accepting nature of the people here.