looking for movie

sooo im looking for a korean movie, i watched it when i was young so my memories are kinda blurry but the story goes like this: theres a guy who has lots of power like a millitary captain or smth and this little girl accidentally bumps into him and he says its ok but then kills her and then there's a poor girl (i think) and one day her twin sister that she didn't know about comes to her house or her workplace. and her twin sister is a brat and says that daddy will come and kill her for reasons i dont remmeber. butttt since they look so alike the father mistakes the mc as his beloved daughter and kills her. the mc being terrified runs off but then she realizes that she can take this as an opportunity to kill that millitary captain (idk how she knows her but she does) because her twin sister is the fiance of the captain. and basically she acts like her twin sister and the day of the wedding she and her friends come up with guns and just kille everyone