Brother Sun Sister Moon

Youta is in high school but his voice still hasn't changed yet. He has a twin sister and her characteristic is drastically different from him. She is a new singer in an entertainment world and she's packed with confidence. Youta admires his sister and thinks he never be as good as her. However, one day his twin sister got ill, and had to have a surgery. So Youta is indirectly forced by his twin sister's manager to pretend to be his sister until his sister full recovery.

This is a story about how Youta going through his self discovery.