Jake Elliott is accused of one count of sexual assault, relating to an offence alleged to have been carried out in the early hours of February 11, 2016.
During the opening of the trial at Sheffield Crown Court on January 16, prosecutor, Matthew Bean, told the court how Elliott, 20, had only met his alleged victim on one occasion prior to the alleged sex offence taking place.
On the evening before the alleged assault, Elliott is alleged to have met up with his victim, then aged 15, and three of her female friends, all 15-years-old, at the Wickersley branch of McDonalds in Rotherham.
He is alleged to have picked the girls up, before the group of five returned to the same branch of McDonald's some hours later.
Mr Bean said: "You will hear evidence from McDonald's manager, Stephanie Allen. She will describe seeing the group there until 4am."
He added: "After leaving McDonald's the group spent some time walking around a wooded area. Eventually, they sat down."
The complainant's three friends subsequently fell asleep, leaving her effectively alone with Elliott, the court heard.
The Crown allege that it was after this that Elliott began sexually assaulting the complainant.
"She told him to stop. His response was to say 'why'," said Mr Bean, adding that he continued to assault the young girl.
The sexual assault is alleged to have lasted for around five minutes, only coming to an end when the complainant physically stopped Elliott.
Elliott's alleged offending was brought to the attention of the police after the young girl told her teacher about the incident. This led to the girl being interviewed, and to an investigation being launched.
"After this, the defendant contacted her on Facebook, demanding to know whether she had gone to the police...the prosecution say he contacted her to find out what allegations had been made to get his story straight," continued Mr Bean.
Elliott denies one count of sexual assault.
The trial continues.