A Nepalese man who spent 15 years behind bars in Japan after being wrongfully accused of murder has thanked supporters who campaigned for him on his first return to the country since his release in 2012.

Govinda Prasad Mainali, a former restaurant employee in Japan who was convicted on the basis of circumstantial evidence of killing a 39-year-old Japanese woman in 1997, also attended a civic meeting to call for the eradication of wrongful convictions.

The 51-year-old said Saturday he has "yet to receive an apology from Japanese police, prosecutors or judges." In an interview accompanied by his wife Radha, he called it "unreasonable and impermissible."

He said he has visited popular tourist spots in Tokyo such as Shibuya and Odaiba during his trip, and wondered "why cases of wrongful convictions could occur in a wonderful country like this."

Although some relatives and friends had told him not to return to Japan as it was "a dangerous country," Mainali decided to visit because he has "done nothing wrong. I wanted to say thank you to the Japanese people who helped me."

After the tearful reunion with his supporters, he said he felt his "wounds will heal a little."

The 15 years of detention have taken a huge toll on Mainali. He has problems sleeping and he stays with his 48-year-old wife "all the time" when they are at home because being alone reminds him of life in prison.

His two daughters, who were a toddler and a baby when he came to Japan in 1994, have both gotten married and now live overseas.

"I wanted to put my daughters on my lap and play with them, but I couldn't. I was deprived of my youth, the most important time of my life."

After returning to Nepal, Mainali plans to set up a nonprofit organization to support victims of wrongful convictions and their families based on his own experiences.

He said he continues to hear from his Japanese supporters about cases of false criminal accusations.

"Why do such problems continue happening? Japanese police and prosecutors must investigate properly by taking due time, and judges must listen carefully. Otherwise, the situation won't change," Mainali said.

Mainali was freed after fresh DNA tests pointed to another man as the culprit in the murder of the woman in Tokyo's Shibuya Ward. He was deported to Nepal after his release.