While Yiren was a prisoner in Zhao, he met a trader named Lü Buwei. Lü knew that, when King Ze went to death, Yiren's father Lord Anguo would be the leader of Qin. Lü also knew that Yiren had many brothers but Yiren's father loved a woman who had no son. Lü worked hard to make that woman adopt Yiren (take him up as her son); Yiren even changed his name to Zichu ("son of Chu") because his new "mother" was from a land named Chu. Lü's design turned out well: he and Zichu secretly went out from Zhao and, when Ze and Lord Anguo died, Zichu got to be the ruler of Qin.