Connor Greer preyed on the child who for years was too scared to tell anyone about her ordeal.
She eventually told a friend, who alerted a teacher sparking an investigation into the abuse.
Greer's victim wept yesterday as she finally saw him brought to justice at the High Court in Glasgow.
The 21-year-old pled guilty to rape and two charges of lewd and libidinous conduct.
A judge told him he was guilty of a "most serious type of conduct" as Greer was remanded in custody pending sentencing next month.
The court heard the attacks repeatedly occurred between 2003 and 2011 at houses in Glasgow's South Side - including Greer raping the girl when she aged 14 or 15. The abuse would often happen at night when Greer would "change".
Greer was also placed on the sex offenders list.