After a fight Hayate, Nagi heads to the apartment complex to hang out.  But her “little sister” is the only one home.  This might be Nagi’s chance to find out what Ruri’s real goal is. 
Why do you say stuff like that?
¿P-Por qué tienes que decirlo de esa forma?
¿Por qué eres tan mala?
Por que você diz isso?