All (registered) residents of Japan over the age of 20 and under the age of 60 are required to join the National Pension system. In order to apply for the National Pension system, please go to the National Pension window at the municipal office where your resident's card is issued.
[Special National Pension Payment System for Students]
For students who do not have an income, there is a "Special National Pension Payment System for Students." For details, please visit the website below:
Japan Pension Service: http://www.nenkin.go.jp/international/english/index.html