A Japanese researcher whose worldview was shaped by a transcontinental journey in his youth has spent years chronicling the lives of Native Americans and other minorities in the United States.

"While moving across the continents to the west, just like a runaway boy, the faces of people I met changed," said Jun Kamata, 44, now an associate professor at Asia University in Tokyo, of his two-month-long trip from China to Portugal in 1990.

Jun Kamata japanese researcher

Attracted by the diversity he saw, Kamata left for the United States after graduating from high school. It was there that he happened to become acquainted with indigenous peoples while studying at a rural community college in New Mexico.

The encounters eventually led him to transfer to the University of California, Berkeley, where he researched the lives of Native Americans, before earning a doctorate in urban planning at the University of California, Los Angeles.

Kamata has visited more than 100 reservations over the past 25 years to hear what Native Americans have to say about their history and present life. He always totes his camera.

"I never learned photography professionally. I put priority on building a good relationship when I visit reservations, and then I just wait for the chance to snap photos," Kamata said.

His interests have expanded to other minority groups as well, whom he also met with regularly and photographed.

He recently published two photographic volumes: "Indigenous Peoples in America: Passing Memories Toward the Future" and "America -- The Pride of Diverse Minorities."

The first book depicts the daily lives of Native Americans living on reservations. While many of them smile in the photos, Kamata explains the severity of their situations in the epilogue.

Japanese researcher sheds light on U.S. minority groups

(Jun Kamata)

Kamata talks about how discrimination by Europeans who settled in the "New World" still affects Native Americans today, pointing out that more than a quarter now live below the poverty line.

"Alcohol- and drug-related crimes, accidents and diseases still threaten indigenous communities," Kamata said. "With their languages, traditional cultures and even human dignity denied, not a few young Native Americans choose to kill themselves in the face of racial discrimination."

Kamata also raises awareness about nuclear facilities, such as a plutonium production plant, being built near their communities, causing concerns about nuclear contamination of their environment.

The second book focuses on sexual minorities in the lesbian, gay, bisexual and transgender communities. There are also photographed scenes of a Latino community in San Francisco, homeless people and remains of wartime internment camps of Japanese Americans.

Japanese researcher sheds light on U.S. minority groups

(Jun Kamata)

In his research of the history of Japanese Americans, Kamata found that they had exchanges with Native Americans through the fences of the internment camps, which were located in the outlying areas near reservations.

After the end of World War II, Native Americans used building materials from internment camps to renovate houses, offices and churches on reservations, according to Kamata.

Circumstances surrounding LGBT people have been changing drastically, with the U.S. Supreme Court recognizing same-sex marriage as legal and deeming state-level bans unconstitutional in 2015. But as U.S. President Donald Trump's recent proposed military ban on transgender service members demonstrates, the battle wages on.

"U.S. lawmakers cannot ignore voices of LGBT anymore at a time when people with various ethnicities and sexualities form a family," Kamata says in the book.

While studying for his doctorate, Kamata lived with Latino immigrants, who were always coming and going from his apartment in the process of building their own lives.

Kamata said the fact that he was forced to speak Spanish and not English with the people sharing his apartment allowed him to relate to a segment of American society that does not speak the dominant language of the country.

Looking back at his quarter-century of research and photography, Kamata reflected on meeting Native Americans -- the oldest residents of America -- as well as newly arrived Latino immigrants.

"I have also met with sexual minorities and homeless people," he said.

He said the experiences helped him "understand the United States more deeply," influencing him similarly to the journey as a teenager helped determine his path in life. One of his observations was that socially discriminated people tend to stick together.

"LGBT-friendly communities, for example, are comfortable also for other social minorities, including the disabled and people of color," Kamata said. "It is a challenge of the United States if or how it will be able to keep and expand such comfort."

He said he will continue to keep a watchful eye on American society, particularly in light of the controversial immigration policies of the Trump administration.