Since the death of "Big Bully", "Hit-Girl" Mindy (Chloe Moretz) has not forgotten her mission of upholding justice and continues to travel through every corner of the city to punish evil. And "Kick-Ass" Dave Lizewski (Aaron Johnson) is willing to accept all kinds of harsh training from the other party in order to form a new partner with Hit-Girl. On the other hand, Marcus (Morris Chestnut), who adopted Mindy, hopes that she can return to the life of a normal campus girl and enjoy a life dotted with love and friendship. Seeing that Mindy gave up her identity as a messenger of justice, Dave had to turn to the Justice Forever League, which was composed of the reformed gangster "Colonel" (Jim Carrey), and a group of losers in life to fight for justice. Meanwhile, Chris (Christopher Mintz-Plasse), who lost his parents, goes berserk and changes his name to "Mother Fu*ker". He gathers a group of desperate criminals and vows to destroy the just cause of Kick-Ass and his partners. The battle between good and evil begins in this city...