Wu Xinjie gets interested in Su Xing when he is able to decipher the Mountain Lake Riddle, something no one had presumably been known to have solved. Wu Xinjie makes a plot to help Gou Zi capture Lin Yinmei so she could replace her as Su Xing's Star Maiden. Su Xing figures this out and states he would not abandon Lin Yinmei for Wu Xinjie. Wu Xinjie redeems herself after she helps them. Su Xing forgives her before asking her to leave them. Wu Xinjie kisses Su Xing goodbye and unexpectedly forms a contract with her.
Being the second girl that he signs a contract with, they are very close and often share their worries and concerns regarding their plans with one another. Su Xing heavily trusts her as she serves as the strategist of the team.