He was a charming boy, baring the same face as that of his shining dear sister. Shy in nature, a total outcast, a pitiful nobody walking behind his sister's shadow like he doesn't exist. The boy himself knows this fact. And he too, knew just how remarkable his sister truly was, glimmering like a true star.
Admiring her and only her, he'd do everything for his angelic sister if it means to become her. If it means acquiring that admirable life full of light and stars, that life of warmth and connection.
If all it takes is to pretend as your superior mirror, the boy can easily let go of his own identity to pursue his lonely wish.