The former Sunderland player, 28, is accused of two counts of sexual activity with a 15-year-old girl.
Judge Jonathan Rose told Bradford Crown Court that the girl, who cannot be named, was a "massive Sunderland fan" who was infatuated with Mr Johnson.
He said the jury of eight women and four men had to consider whether serious sexually activity took place.
The two-week trial heard the girl met Mr Johnson at Sunderland Football Club and they later exchanged phone numbers and sent and received 834 WhatsApp messages in little more than a month.
Mr Johnson then met the girl in his black Range Rover on 17 January last year and signed two football shirts for her.
He admits kissing her during a second meeting on 30 January, but denies any further sexual activity took place.
Judge Rose told the jury that the defence's case was that the girl was a "proven liar who made up the other allegations".
He said the defence claim Mr Johnson is a "man to be believed", who has suffered "irreparable damage" to his career and his relationship with his girlfriend and mother of his child, Stacey Flounders, as a result of his admissions.
Judge Rose said the prosecution's case was that the player, who has admitted being sexually attracted to the girl, is guilty.
He said: "He admits he made contact with her and then met her intending to engage in sexual activity with her.
"He admits that he kissed her."
The judge said the prosecution's case was that Mr Johnson "lied to his girlfriend, to police and to the court".
Mr Johnson was sacked by Sunderland AFC after pleading guilty on the first day of his trial to one count of grooming and one count of sexual activity with a child.
He denies two further counts of sexual activity with a child.
Mr Johnson began his career at Middlesbrough before moving to Manchester City and then on to Sunderland in 2012 and won 12 England caps between 2010-2012.
The case continues.
The judge in the trial of footballer Adam Johnson has begun summing up the case.