Technical internship is a system where trainees enter into employment relationships with companies in Japan and acquire skills that are difficult to obtain in their home countries. Until 2016, most trainees were Chinese, but in 2017, Vietnamese overtook them, and in 2019, Vietnamese accounted for half of the total of about 370,000 trainees. Compared to Vietnamese students who can be seen at convenience stores and restaurants, Vietnamese trainees are a hidden presence with few opportunities to interact with society, but they are rapidly becoming more widespread.