Botsuraku Ririn wa Kyou mo Koukyuu Kouryakuchuu

In order to avenge her destroyed family, Ririn works as a palace maid, hiding her identity as the daughter of a noble family. In order to exact revenge, Ririn learns martial arts, gaining resistance to poisons and assassination skills. However, when she uses her honed physical abilities to save the emperor from peril, he falls for her... (Source: Akita Shoten)