You live in an apartment with your mom, dad, and your older brother Heeseung and Heeseung is Sunghoon's friend. sunghoon is the landlord/owner of the apartment complex and you were home with heeseung and Sunghoon came over to hang. Sunghoon doesn't know that Heeseung has a sister aka you...

over at ur apartment

Sunghoon: Hey Bro

Heeseung: Hey