It was Koreans' love of mountains, especially Baekdudaegan, that has opened doors to him in both Koreas.
That hospitality will be tested next year, when Mr. Shepherd plans to request formally that the two governments allow him to hike the full length of Baekdudaegan. No traveler can legally cross the border without permission from both sides. Mr. Shepherd said that when he recently broached the idea to government contacts in Pyongyang and Seoul, their initial reaction was positive but he was also told that the final decision would depend on the political mood then.
Mr. Shepherd, 47, became a minor celebrity in South Korea after he and a fellow New Zealander, Andrew Douch, became the first foreigners to walk the entire South Korean section of the mountain chain, in 2007, and published an English-language guidebook to the trail, with David A. Mason, in 2010.
Armed with 10 copies of that book and an introduction from the Korea-New Zealand Friendship Society, a nongovernmental group that promotes cultural dialogue between the two countries, Mr. Shepherd arrived in Pyongyang in May 2011. He told officials there that he wanted to do something that, because of tensions on the divided peninsula, no Korean from either side had ever done: document all the main mountains of Baekdudaegan, in both North and South.
(Read more: North Korea Surrenders to Foreign Currency Invasion)
And he was pitching this idea in North Korea, where much of the population suffers chronic food shortages and other privations and where hiking for fun — a favorite pastime in South Korea — is hardly known.
"People go to the mountains of North Korea specifically for a purpose: to move from one village to the next, to go looking for herbs and spices, to go hunting and — where you are allowed to — to go to collect wood," he said. "Literally, North Korean mountains are empty of recreational hikers."
Mr. Shepherd said that North Korean officials seemed to appreciate a foreigner who had come to the North not to talk politics nor to hand out aid, but with a genuine interest in their mountains. As in South Korea, the idea of reunifying the long-divided peninsula has a strong pull among people in the North, and his contacts in Pyongyang recognized the symbolism of his project.
"They thought it was a good thing for the whole of Korea," he said. "I remember one of the military officers saying to the effect that, even though Korea was divided, Baekdudaegan is not, but only a bird can travel freely along Baekdudaegan at the moment."
(Read more: North Korea Says South's 'Sinister' Moves Caused Talks Collapse)
Between March 2011 and July 2012, Mr. Shepherd visited North Korea four times, spending a total of three months climbing and photographing 24 Baekdudaegan peaks. Most were in some of the most inaccessible parts of the world's most isolated country — areas where Mr. Shepherd was certain he was the first foreigner to set foot since the war, partly because, as his North Korean contacts told him, no one else had ever asked to visit them before.
In North Korea, Mr. Shepherd said he could find no experienced hikers. He had to rely on old maps of North Korean mountains he had bought in South Korea.
Local villagers guided him, often cutting their way with machetes through thick forests to the peaks, where he could get the photographs he wanted, of mountains extending out like waves in a stormy sea.
At first, he said, his escorts from Pyongyang could not understand why someone would waste energy scaling a mountain to photograph it. At the base of dark brooding mountains, they would ask: "Why not take pictures of the mountain from here?"
Now back in South Korea, living in a house at the foot of Songnisan, a Baekdudaegan mountain 120 kilometers southeast of Seoul, Mr. Shepherd runs Hike Korea and makes a living photographing and writing about mountains and leading hiking tours.
On July 22, the South Korean MBC television network aired a documentary on his North Korean expedition, which Mr. Shepherd also chronicled in two South Korean magazines.
He is scheduled to return to North Korea in mid-August, with five New Zealand motorcyclists who plan to make this the first leg of a world tour. The bikers hope to cross the demilitarized zone into South Korea on Sept. 4, political conditions between North and South permitting. While in North Korea, Mr. Shepherd plans to exhibit his photographs from mountains of both Koreas, and deliver copies of his new photographic book.
(Read More: North Korea Sends Top Kim Jong-Un Aide to Beijing)
"Although our nation is divided, Baekdudaegan symbolizes the historical and ecological continuity of the peninsula," said Chun Bom-kwon, a director general in the South's Korea Forest Service, which partly financed Mr. Shepherd's North Korea trips. "His work will reaffirm that Baekdudaegan is one entity even though it is cut in half by a fence."
Baekdusan, which means "white-headed mountain," is considered the patriarch of all Korean mountains. Koreans, in both North and South, believe that all the peaks in their mountainous peninsula are connected to the Baekdudaegan range and lead back to Baekdusan.
Each year, thousands of South Koreans make a pilgrimage up the Chinese side of Baekdusan and pray for reunification at the mountaintop lake. In the South, brightly dressed urban hikers offer food and drink at the shrines of the sansin, or mountain gods, along Baekdudaegan at the start of the hiking season.
In the North, Baekdusan features prominently in the government's campaign to incorporate elements of indigenous mountain worship into the personality cult that buttresses the dynastic rule of the Kim family. The "secret camps" that Kim Il-sung, the founder of North Korea and grandfather of the current leader, Kim Jong-un, purportedly established around Baekdusan when he waged guerrilla war against Japanese colonial rule have been preserved as sacred sites. Murals depict North Korean leaders standing against the backdrop of the mountain.
Such lore drives Mr. Shepherd's ambition to become the first person to hike the entire length of Baekdudaegan. Such a journey, he said, could help Koreans affirm their shared national identity after decades of separation that have seen the two sides drift apart in language, culture and economy.
But he remains first of all an explorer.
"It's never been done before," he said. "Any adventurer wants to be the first."