A Japanese doctor is warning Vietnamese people considering traveling to Japan to work as vocational trainees to think twice, saying the system amounts to "slavery" and uses the country's positive image to take advantage of those who enroll.

Junpei Yamamura, a doctor at Minatomachi Medical Center in Yokohama, near Tokyo, produced a 13-minute video in Vietnamese after visiting the Southeast Asian country between May and June to interview four people who returned home after having bad experiences in Japan's vocational trainee system.

In the video, the interviewees, including a 24-year-old man who lost sight in his left eye after an accident while working at a construction site in Japan, spoke of the hardships experienced while working as trainees.

The man said after the accident he was forced to leave Japan by the institution overseeing him and other Vietnamese trainees. He said there were inadequate procedures to allow him to make an insurance claim for his injury and he had to file for compensation again upon returning to Vietnam.

Other episodes unveiled in the video include alleged cases of physical violence and nonpayment for overwork time.

The video was uploaded to YouTube by the Lawyers Network For Foreign Workers, a group which has been working in collaboration with Yamamura in helping foreigners living in Japan.

(Video created by Yamamura)

According to the Health, Labor and Welfare Ministry, about 229,000 people were working as foreign vocational trainees in Japan as of the end of 2016. Vietnamese nationals accounted for the largest single group at 88,000, followed by Chinese at 81,000, Filipinos at 23,000 and Indonesians at 19,000.

While the system of accepting foreigners at Japanese companies as vocational trainees was established with the aim of helping them acquire skills that they could use in developing their countries upon their return, there have been cases of Japanese companies abusing the system as a source of cheap labor.

Yamamura said Japan should "accept foreigners as workers, not as vocational trainees."