When she first met him, she was 12 years old and he was 9 years old. He called her sister, but he was the one who loved her all the way. It wasn't until she was 25 years old, and when he was 22 years old, that he realized that he was no longer the younger brother he used to be. He could love and protect her like a man, but is it really possible for a sister and a younger brother to fall in love? Can you really stay happy? It turns out that love really is a habit, starting from a young age!