Mona and Lisa are a pair of twins that first appeared as the boss fight at the end of the boat stage in the original Streets of Rage. The duo are a pair of highly athletic women whose appearances were palette swaps of the player character Blaze. One twin specializes in throws and the other in jump kicks, but both are highly agile and and to jump and flip out of the way of the player's own attacks.
Mona and Lisa returned in Streets of Rage 3 with a radical visual overhaul. With the new look came a new set of moves including flying spin kicks, a spark attack that runs across the ground and new team attacks.
In Japan, their names are Yasha and Onihime, and they are apparently of Japanese descent.