Sonia Shaflnarz comes from a family part of the Sicilian mafia. She moves to Japan in order to get revenge against the Sanzen'in family, because her father died due to the Sanzen'in family, though not directly. In "Extra- Radical dreamers" of chapter 41, her father hid in a trash can to assassinate
Nagi on Mykonos Island but
Hayate prevented it and defeated him. After that, he quit the mafia and went to Japan to become a cook. Then he died because he didn't know that there was poison in blowfish.
She impersonates
Sister Fortesia, a sister from the Church of Alexander Mark and the Tiger's Pit for Butlers for the purpose of approaching Hayate and the Sanzen'in family. She speaks fluent Japanese, but she uses harsh words and blames it on the fact that she doesn't know Japanese very well. Sonia has unbelievable strength and fighting ability and uses tonfas as weapons.