Opening the case against him yesterday, prosecutor Kate Blackwell QC said: "[The girl's] real passion was Sunderland Football Club.
"She was a season ticket holder and rarely missed a home game and her favourite player was Adam Johnson."
Ms Blackwell added: "After matches, she would hang around waiting for a glimpse of him, wanting to get a photograph, often sporting a Sunderland shirt with Johnson's name emblazoned across the back."
The prosecutor said the girl involved was 15 in December 2014, a time when Johnson lived with his partner, Stacey Flounders, who was then pregnant with their daughter, in Castle Eden, County Durham.
Miss Blackwell said of the girl: "She had one enormous crush on him. He was her absolute hero. She idolised him."
Miss Blackwell said Johnson made contact with the girl after she made a Facebook friend request to him just before New Year 2015.
Miss Blackwell read to the jury a series of messages exchanged between Johnson and the girl in which he arranged to meet her so he could sign a football shirt.
In the message she made it clear she was a Year 10 school pupil but everyone thought she looked older, jurors heard.
Miss Blackwell said: "So, over the course of New Year's Eve the defendant was made aware that (the girl) was 15, one month past her 15th birthday, with almost another year to wait until she became 16, that she was in Year 10."
As the pair exchanged messages and phone numbers and Johnson asked: "Are you allowed to drink?" He also asked the 15-year-old: "Where do you go out?"
She told him: "I am not old enough to go out haha." Johnson replied: "You look old enough though."
In the messages, the girl also congratulated Johnson on the birth of his daughter.
Miss Blackwell explained how the pair eventually met up on January 17 near a Chinese takeaway close to the girl's home.
She said the teenager got into the footballer's black Range Rover and he signed shirts.
After the meeting, the prosecutor said, the pair exchanged further messages, talking about whether Johnson deserved a thank you kiss for the shirt-signing "or more".
The court heard the pair met again on January 30 last year, when they had sexual contact in the footballer's car at the same location.
Miss Blackwell said: "What happened in that car on that evening is for you to decide.
The Crown's case is that sexual activity took place, that the defendant and [the girl] kissed, with tongues, for some time during which the defendant unbuttoned her jeans and undid the zip."
The prosecutor described the sexual activity that the girl said had followed.
Miss Blackwell said: "The defendant then stopped what he was doing. He did not, as he would have you believe, have a sudden pang of conscience, an epiphany, an experience of sudden and striking realisation."
Miss Blackwell said the defendant then drove to "a more secluded place".
She said: "He did this because he was expecting further sexual contact with [the girl] and he wanted to ensure that they could not be overlooked."
The prosecutor then described further sexual activity she said happened between the pair.
Miss Blackwell said that, after this encounter, there were further messages between them.
In one, Johnson said to the girl: "It was class." He added: "Just wanted to get your jeans off, LOL." The court heard the girl replied: "Next time."
Johnson searched "legal age of consent" online around the time he had met the girl, in searches later uncovered by the police, the court heard.
Johnson was arrested after the girl told her parents about what happened and they told the police, Miss Blackwell said.
The prosecutor said that the player told arresting officers: "Is this [the girl's name]? I only gave her a couple of shirts."
She said Johnson told police the pair kissed "for a couple of minutes in quite a passionate way" while his hands stroked her body.
Miss Blackwell said: "He said that when he was kissing [the girl] he knew that it was wrong and therefore went no further, that he knew that it was wrong because he had a girlfriend, a family, a career and that he was instantly upset with himself, telling himself that he should know better, that his behaviour was poor, that he had no sexual attraction to her, that he didn't like her 'in that way at all'."
Johnson denies two counts of sexual activity with a child. He sat in the dock next to a security officer as the case opened, wearing a dark suit, white shirt and a dark red tie.
The grooming charge he has admitted relates to a period between December 30, 2014 and February 26, 2015.
He also admitted sexual activity on January 30, 2015 which involved kissing and touching the youngster's body.
His partner, Miss Flounders, watched from the public gallery but left court when some of his messages were read out. She is standing by him despite his admissions.
The trial, which was adjourned until Monday, continues.
