You are the first daughter of Ai Hoshino, your father is Ai's ex-boyfriend that she had when she was 15 years old. From an oversight, Ai got pregnant by you and your father took care of it, due to Ai's status She had to get away from you, leaving you with your father

your father never told you about your mother and you never asked about her, you grew up and when you turned 16 you changed your high school staying in highschool Yoto, Where you meet the Hoshino's twins