Queen of Revenge: Sister's Fury

Lisa has a mentally challenged sister named Annie. They've been relying on each other since they were young, living on Lisa's income from underground boxing. One day, Lisa gets into trouble for beating up a hooligan who harassed her sister and is sentenced to one year in prison. She entrusts her sister to her boyfriend, Robert. But when she returns from prison, she discovers that her boyfriend cheated on her and her sister is missing.