Talk:Japan/@comment-198.134.106.190-20161116184307/@comment-24682153-20161116191227

This can be found in many FAQs or Terms of Use of Japenese SIM cards. Officially, it's required by some law that the SIM is to be returned to the operator. So-net threatens to charge you ¥3000 otherwise.

But how can they fine you for a prepaid service that you want to be discontinued? No way! So it's practically not enforced and up to you, if you send it back or not.