Leone is one of the older members of the assassination group, Night Raid. She has a very relaxed and cheerful personality, tends to display a lack of ladylike manners, such as shoving Tatsumi into her breasts, putting her feet on the table, or consuming large amounts of Sake. She serves as a sort of big sister figure to Tatsumi and the younger members in Night Raid, often referring to herself as “onee-san”. Despite the morally dodgy nature she can sometimes display, Leone is not one to tolerate injustice, and can be especially vicious to those who commit the most vile acts. She excels at gathering information and exercising calm judgement when necessary.
In the last episode, Leone is stripped of her powers by the prime minister’s imperial arms and was shot in the stomach several times, surviving by will alone, Leone kills the Prime Minister and shortly after dies a peaceful death.