Ren Yuxuan is a girl with an eccentric personality, but in everyone's eyes she is a "good girl". By chance, she met Long Kairi through Yiyi, but she did not expect that he was Yiyi's brother. When she and Long Kairi went from strangers to falling in love, a third party suddenly appeared - Xiaosong. Ren Yuxuan didn't know that he was her best playmate when she was young and that they had made a promise. The ending suddenly took a 180-degree turn. Ren Yuxuan died mysteriously in the end...