IN JUBA, SUDAN Abraham Akoi strolled confidently through a door marked with a sticker that read: "Secession."

The tall, rail-thin D.C. resident walked up the stairs of the Ministry of Finance here in southern Sudan, entering a world he had never expected to enter.

As he walked into his office, another man smiled and declared: "Separation!" Hazy sunlight glinted on the man's purple-shaded thumb, a sign that he had just voted.

That morning, Akoi, too, had taken part in Sudan's historic week-long referendum, which ended Saturday. He had voted for the south to secede from the north, as most people in this region were expected to do.

For Akoi, it was the latest stop in an extraordinary journey. It began with a dangerous walk across mountains and deserts when as a child he fled a civil war. It stretched to refugee camps and prestigious American universities and now unfolds back here amid great hope and trepidation over what could soon become the world's newest country.

"I still can't believe that I am here," said Akoi, 31.

Ten years ago, Akoi stepped off a plane in Atlanta, one of several thousand "lost boys" whose hardship and escape from Sudan's brutal 22-year conflict captured the imagination of Americans. Thousands of southern Sudanese were resettled in the United States, and most struggled to blend into their adopted communities. But many, like Akoi, excelled.

Akoi earned a degree in history and economics from the University of the South in Tennessee, then a master's degree in government and an MBA from Johns Hopkins University. He had internships at the Carter Center in Atlanta and with Rep. Donald M. Payne (D-N.J.), who has championed causes in Africa.

Today, Akoi's life has come full circle. Southern Sudanese living in the United States could have voted in several U.S. cities. But Akoi and many other "lost boys" chose to return to their homeland to vote and help propel it into its next era.

"It is a fulfillment of a mission we for so long have yearned to accomplish," said Valentino Achak Deng, whose own journey was portrayed in the novel "What Is the What." "It is a day when I feel like someone has finally given me my voice. It was important for us to be here, to be on this soil."

'Thinking about the past'

The day Akoi voted, the memories flooded back: fleeing his village at the age of 11. Walking, hungry and tired, to neighboring Ethiopia. Fleeing militias and bombers. Then returning to southern Sudan, only to flee again to a refugee camp in Kenya. Learning that his father and three brothers had died in the war.

As he stepped up to the cardboard booth to cast his vote, his hands shook.

"I was thinking about the past, all that we've been through," Akoi said. "I voted on behalf of all who lost their lives. I voted for my brothers."

He paused and added: "I looked at the ballot for a few seconds, as if it would fly away, and then I dropped it into the box."

In a couple of weeks, he'll know whether his dreams of secession will come true. If the referendum passes, as expected, southern Sudan will declare its independence in July.

On a recent day, Akoi drove through Juba. He noted how much the capital has improved since his first visit back, in 2009.

A few years ago, "this road was not paved," he said with pride.

He pointed at a sign for a local relief agency: "That was started by Sudanese in the U.S.," he said.

Akoi knows that significant challenges lie ahead. So many key issues dictating the relationship between north and south remain unresolved. Will the oil-producing border region of Abyei, contested by both sides, erupt into war? Will revenue from Sudan's massive oil reserves, the majority in the south, be shared equitably?

"Our political and financial institutions are weak," he said. "Civil liberties are not strong. There are no good hospitals and no good supply of medicines.

"And only 15 percent of south Sudanese know how to read and write. That's not very good for democracy."

Like most southern Sudanese, Akoi blamed Sudan's government, which is dominated by an Arab elite, for the region's woes. For decades, the Khartoum government sought to repress the south. Akoi noted how the vast majority of universities were located in the north. "We can't have good governance if the institutions of higher learning are not there," he said.

Akoi has already begun playing a role in shaping his homeland. He has declined to seek the six-figure salaries in the United States that come with earning an MBA. Instead he has chosen to live here and work with the government. His current job in the Ministry of Finance is to make sure government ministries and departments spend money efficiently and according to the annual budget.

Water and mangoes

It's a delicate balancing act. The government is led by and filled with former rebels who have little experience. Corruption is rife; jobs are often handed out based on tribal allegiances. And despite his history, many perceive Akoi as an outsider.

"How do I tell them what to do without them thinking that I am some guy from the U.S. talking big? It's a very tough job," he said.

A few months ago, as global oil prices fell, he told officials they had to cut spending.

"They were not happy, but I had to do it," Akoi said. "They didn't understand that the oil revenues were based on market prices. They thought they would always get the same price."

Salva Kiir Mayardit, south Sudan's president, has tapped Akoi to become the deputy director of administration and finance - a sign that the government is reaching out to qualified technocrats in the diaspora. Many of southern Sudan's educated professionals, including lawyers, doctors and economists, died in the war or fled the region.

Akoi vowed not to be influenced by corrupt bureaucrats.

"I have a commitment and integrity to do the right thing for south Sudan," he said. "Our biggest challenge is creating a system that is bigger than one person, to create a system that will stand the test of time."

On most weekends, Akoi walks along the banks of the Nile, which snakes through Juba. When he looks at the lush mango trees, he sees the potential for southern Sudan to export their fruit. When he looks at the brown waters, he sees the potential to harness hydropower to light up the electricity-starved region.

"When I look at the water and the mangoes, they are indicators of how beautiful south Sudan is," Akoi said. "This is a place where people should not go hungry. If you plant anything here, it will grow."