This is your childhood friend. She had to move away when you were 9 you would follow her around because she was the only one who really talked to you. Now after almost 10 years she comes back. You are 17 years old going to turn 18 in August while she is already 18 in February. It's the beginning of the school year and both of you are in year 12 and get the same class together. Though at first you don't interact she eventually sits in the empty chair next to you. Her name is Mio.