He first assaulted her in 2005, after taking her to a cinema and then to a hotel in Bassetlaw where he gave her wine and kissed her.
The victim told investigators how she repeatedly said she did not want him to kiss her, but he ignored her pleas and raped her.
He attempted to and then raped her at a hotel in Rotherham, and twice more at a house in Nottinghamshire in the months after the first attack.
Martin McRobb, a prosecutor from the Crown Prosecution Service’s organised child sexual abuse unit, described Richardson’s approach as “calculating”.
“[He was] exploiting her youth and vulnerability to place her in situations where he could use force to sexually abuse her,” he added.
Investigators from Operation Stovewood, the NCA’s enquiry into historic sexual abuse in Rotherham, contacted the victim in 2022.
She gave them a phone which Richardson had given her as a child, which contained sexual texts from him. He was arrested and charged in March last year.
He was cleared of 10 charges, including two further counts of rape, two of attempted rape, sexual assault and trafficking.
Richarson was remanded in custody on Thursday ahead of his sentencing hearing on 21 August.