Is it permissible to do an internship there as a foreigner?
If the companies advertise such a job, then you can of course try to apply there - condition, you have a valid work permit. You can get it for example with the Working Holiday Visa - everything else would be too much for an internship.
But I have to say, internships, as known in Germany, are not available in Japan.
The Japanese working world does not work that way. This must be a very international company, if something like an internship (and then an international) should be offered. For example, Bosch is a well-known example here; They regularly offer international internships for foreign students.
Otherwise: What did you study? How is your Japanese? Did you use the WorkingHoliday visa already?
Take a look at international internship exchanges that relate to your degree program. Maybe you have success.
As already mentioned, it could be difficult for large companies in this field if they do not offer internships on their own, simply because the internship culture in Japan is by far not as pronounced as in Germany. However, I have just heard in the IT field that even unsolicited applications have been successful and have even led to a paid (!) Internship. It applies as almost always in life: you can try it once:-)
However, some who come on the Working Holiday visa work at smaller companies as a game tester and do there u.a. Translation tasks.
