Hi,
We have just released the newest patch earlier today. Did the same issue happen in this patch?
Viewing post in Villainess x Reborn (Early Build) comments
If you are redirected back to the menu after the convo with the brother before the ball, that means you have reached the end of the intended content. We have only streamlined the game up to that scene. You can play through the later scenes, but you might experience bugs. We will be working on those content next.
Feel free to load any save files to replay any parts of the story. Hope that helps!