When publishing papers on open access (OA) repositories such as institutional or subject repositories, you can make your works available online at no cost (self-archiving) without paying Article Processing Charge (APC). This is referred to as Green OA.
In addition to papers you are about to submit, previously published works in academic journals can also be made open access retrospectively.

However, when making research outputs published in academic journals available as Green OA, please note that publishers may impose various restrictions. These could include the specific versions of the manuscript permitted for public release or embargo periods during which public release is restricted. Be sure to check the terms of the agreement with the journal in which the paper was originally published.

For details on registering your works with Waseda University’s institutional repository, please refer to the Waseda University Repository.

Waseda University Repository