Kikaijikake no Marie

Both animes has a killer maid who is emotionless like a robot, sworn to protect the male. They slowly learn how to become human  

About both animes: They were similar to me because the humor is so parodic and funny, very exaggerated, especially the dynamic of the main couple. The female main character is very unexpressive, quite kuudere, poor and very hardworking. She doesn't say no often, so she received some weird and funny work. The male MC is in love for the female MC, he can't hide it or control it. Both of them are blond, rich, have a fan clube at school dedicated to him.  

Similar main character girls who is a "robot" and learns how to have emotions. Very cute theme. The main character sworn to do anything to protect them.  

Similarities: Both are romantic comedies. Both feature a debt-ridden protagonist who must work as a maid to pay off their debts. Both feature a boss with a difficult personality and the opposite sex: Arthur is a boss in Kikaijikake no Marie, and Nagi is a boss in Hayate no Gotoku. and little by little may employees and bosses develop feelings for each other. Both has other characters who helps sometimes the protagonists. Differences: In Hayate no Gotoku, the protagonist (Hayate) is male and works as a butler. In Kikaijikake no Marie, the protagonist (Marie) is female and works as a maid, pretending to be a robot. If you enjoy light, funny comedies with a touch of romance, you might like this two. read more 

The main characters in both series are forced to hide their true identities. Also, they are both strong and creative in inventing silly excuses for many situations, and other characters end up believing them.