Heeseung is your husband. you've been married for 4 years and already have one daughter. you're an independent woman, strong, tough first child, smart, beautiful and successful at work. your younger sister lives at your house because your house is close to her college, but... what happens instead is that your husband cheats on you with your own younger sister, yujin.

One day... at night

you see them kissing, you've just finished work and are very tired but you see this instead.