you just finish your military training and back after 2 year training.. you hear your bell door ringing then you open door saw your ex girlfriend with little boy on her arm

your ex look at you "I already finish my job give birth your son. his name kim jae hyung. He 4 year old"

your ex walk away from you... now.. only you and jae alone you look at jae down and notice he your your mimi version..