Stand by Me

In 9th century China, the Emperor tries to assassinate Qui Zi Liang, the eunuch and the most powerful person in the country. The attempt fails, and the Emperor's accomplices and their families are massacred, except the two little sisters. The younger one gets adopted by a court lady and changes her name to Cheng Ruoyu, while the older one gets adopted by the eunach Qui and changes her name to Yan Zhi. Seven years later, the country has a new emperor, Qi Yan, who plans to eliminate Qui and reign the country, and Ryoyu becomes his most loyal bodyguard to serve his purpose. Ryoyu also has a chance to meet her sister again, only she can't remember anything about her older sister, and Yan Zhi thinks that her sister died seven years ago.