Yuuki Erina

A first grade high school student. She is the eldest daughter of the Yuuki family. Even though she was really close to Keita when she was small, recently they talk less and she always acts cold toward him. It's because she's at the age of puberty, and also that she looks at her brother as a man. She fell in love with him and is confused about what to do. She is always worried because she can't consult about it with anyone.