Hayate is forced into a situation his only viable option is to do something illegal, unethical, and unbecoming.  After being called a Mom like figure to Nagi, Maria goes to the source on information regarding Nagi’s father.
I'll take care of your little sister.
Yo me encargaré de tu hermanita.
Yo me encargaré de tu hermanita.
Eu vou cuidar da sua irmã.