I think that it was tattooed on her previous body. The current body is already transforming into the original one from the start (like the mole under her eye I think? It has been too long since I read this in raw so I don’t remember clearly) But it is sure that the current body has already become Z’s.

This novel iis indeed a GEM!!! True, it has typical genres such as reincarnation, CEO ikemen but this actually has good plot, dynamic couples, and great amount of hidden plot twists. You won't be didisappointed reading this.