Heart of Glass-born in shadows, left in mist |Shuntaro Chishiya x fem oc

Mayuka Yaba is a regular high schooler with a somehow questionable past but still a happy life. However looking in the mirror shows her a face of two people she never met. She is happy with her adoptive family even though her current family keeps secrets about her actual family causing her to stop questions at some point. Mayuka was always good with people and their emotions, she's intelligent and caring.
It was a normal day at school when suddenly everyone disappeared and she's left alone with her best friend Akira. They find themselves in a world where they have to play deadly games to survive. One day they meet a young man who takes both of them with himself to 'the beach'. At that point Mayuka didn't know how much that guy would change her life. Being away from her parents brings the questions up again. Who is she really and why all the secrets? If that's not enough already, there are even more challenges for the girl. Betrayal, confusion, secrets.. Death.