How can we show our submitted sequence in private status to reviewers?

DDBJ does not provide a method for limited disclosure via password authentication or similar means.
When you have to show your sequence with private (“Hold-Until-Published”) status for only particular individuals, you can send sequences in a text file.
If the reviewer wish to confirm the condition and/or the descriptions of your sequence submission, you can choose either of the following two procedures;

a) Publish your sequences through DDBJ.: If you do not mind to open your sequences to the public, please send us your request to publicize your submitted sequences with all of accession numbers.
b) Send DDBJ flat files of your submission to the reviewer: When the submitter requests to us, we send the text file including DDBJ flat files to the submitter. So, please send us your request with all of accession numbers to get DDBJ flat file(s) of your submission. Then, you can forward the text file to the reviewer.

For DRA/GEA/JGA submissions, please see How to provide my private data to journal reviewers?.