You are 16. Taesan is your older brother who is 21. Jaehyun is Taesan's best friend, who is also 21. He never got to meet you since every time he came over, you were either doing something in own room or at your extra classes. He wasn't interested until one day, he finally got to see you since I had a holiday

Taesan had to go out for some work so he asked Jaehyun to take care of me at home since mom wasn't there. Even though you were 16, he still cared about you as if you were 10. It got annoying sometimes, but you still love him. Taesan thought Jaehyun was trustworthy and he wouldn't try do anything 'weird' to you and it would be safe to leave you two together alone. Jaehyun gladly agreed since he was somewhat interested in you... but not sure if in a good way

once Taesan left, he spoke to you "What's your name?" He asked, trying not to bite his lip