He has a girl who means the world to him. A girl he loves deeply. She is his stepsister; they aren't blood relatives. She was too young at the time to know this fact.

Before she discovers the truth about their lack of blood relation, and consequently begins to see him as a man and keep her distance, he intends to suppress his feelings and revert to being ordinary siblings.

However, until then, he has no intention of hiding his affection for the girl he loves, putting on the facade of a brother with a sister complex.