Hi
EUNJI SON •,
Welcome to Micrsoft Q&A forum and thanks for using Azure Services.
As I understand, you want to only access Azure SQL DB Read Replica, not primary.
Users on the source server are replicated to the read replicas. You can only connect to a read replica using the user accounts available on the source server.
Next you may refer to https://www.ozkary.com/2021/01/create-read-only-user-on-azure-sql.html#:~:text=To%20make%20this%20user%20read,the%20read%2Donly%20user%20account. for creating read only user for your Azure SQL DB Server.
Let us know if this helps. Please reply if the ask is differently understood.
Thank you.