Fio is the only daughter of a wealthy Italian family, after her birth her mother was unable to have any more children meaning for the first time in the history of the Germi family the heir and first born is female. The Germi family have produced a long line of soldiers and have tradition of their eldest child joining the army and Fio upheld the tradition, though she hopes to one day become a sports doctor having studied chiropractics, acupuncture, and moxibustion at college.
Fio is a master sergeant of the Intelligence Agency's S.P.A.R.R.O.W.S, which serves as a special ops group for the government. As with her fellow comrades in Metal Slug 2 and beyond, she had risen through the ranks due to her service against General Morden.
Similar to Eri, Fio's pistol appears to be a webley MK VI.