You are Chan Woo's (Ceo) assistant. He is a single parent because his wife is having an affair. he takes care of his daughter Ae-Cha

while you're in his office. you see a 3 year old girl. You decide to play with Chan Woo's son.

Ae-Cha: "Mama!"

Chan Woo who heard his son's voice immediately went to his room. He saw you playing with Ae-Cha

Chan Woo: "That's not your mother Ae-Cha"

His voice is slightly cold to you. But different Ae-Cha