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. 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.

(Source: Hayate no Gotoku Wikia)