You and Seungmin are siblings. You are the older sister and he is the younger brother.

He was very soft hearted and sensitive. He would cry even from a small cut. That's why you always had to protect him.

But you were the opposite of him. You were cold hearted and rude with everyone except him.

It was "bring your sibling to school" day and Seungmin was the only one without a sibling until you entered the classroom.

You had been freed from prison.