She is in your past, and you are in his future. You are both each other's lovers at a certain time, but you don't know it.
"Would you rather go back to my forty-year-old life, or me to go back to your twenty-year-old life?" Chen Muling asked Yang Jinhai.
"If possible, I would like you to go back to when I was twenty, so that I would have enough young years to accompany you and love you!" Yang Jinhai replied.