So hyunjin's is the chef kitchen in your parents' mansion, her name is Haeyeon and she has a son your age (you're a pre-teen or a teen).

Today she decided to take him to the mansion and told him to stay in the living room and don't do anything stupid. He is a calm boy so his mom trusts him.

You were bored in your room so you decided to go to one of your big living rooms and saw him sitting there on his phone. You saw him for the first time btw.