Prosecutors said the former Sunderland winger “abused his revered position in society” when he had sexual contact with the teenager “in a way that he knew was both morally and legally wrong”.
The girl had contacted the player, aged 28, via Facebook, a jury at Bradford Crown Court heard, and the two began exchanging messages before they finally met so he could sign shirts for her.
After this first meeting, the two joked in their messages about whether Johnson deserved a “thank you kiss” and they met again.
Prosecutor Kate Blackwell QC described how the two engaged in sexual activity in the player’s black Range Rover at this second meeting on January 30, 2015.
Ms 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 what happened next between the footballer and the teenager and 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.”
Ms Blackwell said the defendant then drove to “a more secluded place”, where further sexual activity took place. She told the jury of eight women and four men that the pair exchanged further messages after the encounter and Johnson told the girl: “It was class.”
He added: “Just wanted to get your jeans off, LOL.”
The court heard the girl replied: “Next time.”
Ms Blackwell told the jury: “It is the Crown’s case that what has brought the defendant to this courtroom is a sexual desire for [the girl], an excessive arrogance and an unwarranted level of expectation.
“He has abused his revered position in society and, having met [the girl], this 15-year-old girl, at Sunderland Football Club and later on social media, and knowing that she looked up to him, made a conscious decision to act in a way that he knew was both morally and legally wrong.”
The prosecutor said that in December 2014, when the pair first made contact with each other, Johnson lived in Castle Eden, Co Durham, with his partner Stacey Flounders, who was pregnant with their daughter.
Ms Blackwell said the girl was a passionate Sunderland fan and Johnson was her favourite player. “She had one enormous crush on him. He was her absolute hero. She idolised him.”
Ms Blackwell read to the jury a series of messages exchanged between Johnson and the girl. In the messages, she said, she made it clear she was just 15.
In the messages, the girl also congratulated Johnson on the birth of his daughter.
Ms Blackwell explained how the pair first met on January 17 near a Chinese takeaway close to the girl’s home, and he signed two shirts for her.
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 prosecutor also told the jury that Johnson had researched “legal age of consent” on the internet.
She said: “The Crown suggest that such a search to satisfy such an interest is unlikely to have resulted from a kiss and no more than a kiss, as the defendant contends.”
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. His partner, Ms Flounders, watched from the public gallery.
Ms Blackwell told the jury that Johnson has already admitted one count of sexual activity with a child and another of meeting a child following sexual grooming.
She said: “The Crown’s case is that he is guilty of further and more serious sexual activity.”
Johnson was arrested after the girl told her parents about what happened and they told the police, Ms Blackwell said.
The trial was adjourned until Monday.