『x理论y理论z理论的区别』介绍:Gyeong-ahworksasacaregiverandlivesalone.Theonlyoneshecanrelyonisherdaughter,Yeon-su,butit’shardtoseeheraftershemovedoutonherown.Meanwhile,Yeon-su,whoissufferingfromherex-boyfriend,Sang-hyun,argueswithhimagainandvisitshermother’shouse.AfterYeon-suleft,Gyeong-ahreceivesashockingmessagefromastranger.