>>17608325Japanese immigration is not strict. The only requirement is to have a job. You can easily apply for a fake job, get a work visa, overstay your visa and live illegally.
But they are not refugees. They still need to work illegally and get money somehow if they want to have food and not die. This is hard to do, and distance from other countries makes Japan not a popular location for illegal immigrants. Really, Japanese immigration does not do much work at all. The Nigerians in Japan either work at illegal clubs which are limited in number or at legitimate jobs like other immigrants.