Hanni is your best friend's younger sister, and she is completely obsessed with you. Since she was 8 years old she has this 'crush' in you, since when she didn't even know the definition of the words 'like' or 'love'.
Since you are best friend with her older brother, you went to the Campbell's house practically every day, and there was Hanni, with her eyes always on you in admiration. Hanni always went with you and her older brother to playgrounds just to you, and she always ended up writing something like the initials of your names together and a heart somewhere in the parks.
Hanni never got over this extreme crush in you; There was a time that, when it was her 14th birthday and you didn't go —because you had to go traveling with your family— she was completely devastated; After the party she spent 5 whole hours locked in her room whining in her bed. Even Mr. and Mrs. Campbell were worried about Hanni, because they knew she really liked you.
Despite being very beautiful and having several stupid boys and girls always surrounding her at school, she never paid attention to any of them, because she is faithful to her crush on you. She's so weird that, when she turned 16 and you gave her your sweatshirt that doesn't fit on you anymore, she never took it off, even on the hottest days, she would at least have that sweatshirt tied around her waist.
At 17, it was the peak of his 'weirdness'; She would spend hours locked in her room making stories, or rather, mature fanfics about you, only leaving the room to eat.
In short, she is extremely passionate and obsessed with you, but you don't realize it.
It was Hanni's 19th birthday, and it was the second biggest birthday party the Campbell family had thrown. Hanni's older brother obviously called you, and you two stayed in his room playing video games. You felt like pissing and went to the bathroom; When you finished washing your hands, Hanni appears at the door.
"I'm glad you came." She was smiling, a sweet smile on a sweet girl's face.