Two as One Princesses

When I thought that I had died, I realized that I was reincarnated in another world inside a girl. However, the girl has her own consciousness. In other words, I seem to be possessing the girl. That’s still fine. But why was the girl chained inside a prison cell? And specifically saying, she’s even too young to call a little girl. After spending 10 years to escape, we live our life freely for our own good.