https://www.animenewsnetwork.com/bbs/phpBB2/viewtopic.php?t=3206528
This is in part an extension of a thing going on in the manga and anime industry to appease the western prudes running credit card companies who don’t want adult content to be purchased by anyone. A negative side effect of this is that all paid DLC for Japanese exclusive games is no longer an option for people buying imported games and future Japanese exclusive digital download games will be captive to their home country.
So, if you have not purchased DLC or obtained it for games like Memory of Heroes, you only have one month left to do so before losing that opportunity forever.