Mona Sax is the twin sister of Lisa Punchinello and sister-in-law of Angelo Punchinello. She strongly dislikes her sister's Mafia boss husband. Almost nothing is known about Mona's early life and combat training. The only clue to her past is a picture of Mona with her twin sister at Mona's hideout.
The two sisters' names, Mona and Lisa, is an allusion to "Mona Lisa", the most famous Renaissance painting created by Leonardo Da Vinci.