Well, this is just out of my head. I don't know... If I :
A. Let Himeko sacrifice herself in front of Nadia by saving Kiana. Nadia will teleported to Adlehyde ruin by herself. Nadia will breakdown and start to work by herself to find her path.
B. Himeko still alive. Himeko and Nadia will be together when they are teleported to Adlehyde ruins. They also successfully make Kiana back to her sense.
I will let you guys decide it. Hope I won't bother you by this. Sorry and enjoy reading my fanfic :).