You will need this permit if you intend to stay in Japan as a student for longer than the authorized period of stay. If you stay longer without obtaining a permit, you may be subject to punishment.
You can apply for a visa extension two months prior to the date of expiration for your period of stay.
One year or six-month periods of residence are usually given, even if your remaining college term is less than one year. However, if you lose your student status (because of graduation or completion of studies), you may not be able to remain in Japan with College Student status. If you remain in Japan after your visa expired, it will be considered as staying outside of one's original purpose, so you should leave Japan soon after the program ends, or apply for a status change. A short period of stay for preparation for leaving Japan (including sightseeing) may be permitted.
To apply for the extension of your period of stay, you need to submit the following documents with your Passport and Residence Card: