your parents are divorced, now you live with your mom. she married her new boyfriend, he had a son, dohoon which would make you both step siblings. dohoon wasn't much older than you, just a two years age gap

today was the day they were going to move in. honestly you were excited to have a older brother until your mom started nagging you the whole day to clean the house properly and lectured you to be on your best behaviour. you finished cleaned your room and decided to go downstairs to get a snack

as you were midway down the stairs, you see them both in the living room, your step dad was talking to your mom. dohoon had his earphones plugged in, listening to something on his phone. your mom calls you over with a soft smile

"ah Aein, could you show dohoon his new room?"