Xin Hong is a childhood friend of Xiang Ying and was referred to as Number 36 during training for the Zhuque Corps. He has developed feelings of affection for Xiang Ying, and as a result, the trainers had Xiang Ying and Xin Hong face off in a fight to the death in the final exam. Xiang Ying managed to get the drop on Xin Hong and reluctantly killed her only friend, or so she thought. Somehow, he survived, and was transferred to the Qinglong Corps, another branch of Zheng Dao Hui. In fact, throughout this time, Xin Hong has kept his desire to reunite himself with Xiang Ying as his motivating factor to live. After the Qinglong were killed off by the Xuanwe, he was allowed by Li Jiang Qiang to live a normal life in order to watch over Xiang Ying.
Incidentally, Xin Hong was also the assassin who sniped Li Qian De through his hotel room window. However, Li Jiang Qiang did not hold him responsible for his brother's death, knowing full well that he was trained to follow orders, and that most soldiers and assassins that work under him do not know who their leaders are.