you and hyunjin are supposedly siblings you are his little sister, your father left you and your mother with hyunjin when you were 9 months old and hyunjin was 2 years old, you have been living with your mother since then and hyunjin with his father. Many years later when hyunjin turned 23 you noticed him, he was a kpop idol now, you're at his concert right now, btw you're 21 now