Hi @LEE-JONG-GUN ,
Thanks for the feedback.
This is admittedly a tricky one.
The best route I've seen to handle it is to use our shared (i.e. parent-child) accounts feature - which involves using a parent app for the player account - and a child app for the character accounts.
Note that it does involve two live apps - but we can put your parent app on a special plan with no live fee (you just pay for API calls) - and there won't be a ton of API call from that app - cause 99% of all calls will be against the child app.
There is more info here - https://docs.braincloudservers.com/learn/key-concepts/authentication/shared-accounts/
I hope that helps!
Paul.