how to add Japanese address to old bp master

After setting ‘K’ for Kanji in table TSADV we are able to create a Japanese address for a BP beside the English address data.

BP has one BP number and one address number in table ADRC. The Japanese address has the addional ‘K’ in field Nation. I think that’s fine.

My problem is: How can I add an international version like ‘K’ to business partner which are already exists in the SAP system?

When I take transaction ‘BP’ or ‘JGZ21’ the address field are not open. We have an agreement to do address changes by using transaction ‘JGA0’.

But here is not a possibility to go to the Japanese version.

If some experts know how to add Japanese address to old BP master. Please help.

Regards