FANBOX and pixiv are Japanese-run services, and the Terms of Use and Guidelines for these services are based on Japanese law and legal precedent.
In general, Japan allows freedom of expression, but in some cases, R-18 content will need to be reviewed and censored (posted to a limited audience).For details, check the guidelines below.
https://fanbox.pixiv.help/hc/articles/13239721816217
Uploading a large file to a site other than FANBOX and sharing the link without properly censoring the adult content is in violation of the Terms of Use, and may result in the suspension of your account.Please take a good look at the Guidelines and apply them to your work.
We must enforce these Terms of Use to maintain a safe space for all our creators.Thank you for your understanding.
*Reference link: About adult content