The Wig (2005)

When Chi-Hyon takes home her young sister, Su Hyon, a terminal cancer patient, so that she can help her enjoy her remaining time on earth, she buys her a wig to mask the effects of chemotherapy — not realizing that the wig is, in fact, demonic. Once in possession of the wicked hairpiece, Su Hyon begins committing all sorts of transgressions, including causing Chi-Hyon to have a car accident and trying to seduce her boyfriend.