Undercover Swordsman (2005)

In Ming Dynasty China, the very young Emperor Zheng De is a fun loving person who is always searching for more excitement to overcome his boredom. His uncle, Prince of Ning takes advantage of this offensive attitude of his and secretly starts a revolt against him. In order to control the situation, some undercover agents are sent by the Imperial Guards Commander General Yu Hao Cheng to spy on the prince and report his activities, but all are soon killed when their identities were revealed. Yu Tian, the General's step son and a brave swordsman, is now their last hope to save the kingdom. He is sent under the pseudonym Murong Zhen to Ning Wang, but there he finds out that he has to deal with a greater challenge as he falls in love with the Prince's daughter Xiao Ying.