Nineteen year old Martin Scougal of Old Town, Ayton, admitted raping the nine year old on various occasions between July 2006 and July 2010 at an address in Eyemouth and also to molesting another girl, aged eight.
Scougal now faces sentence for the offences which were carried out when he was 14.
The rape victim, now 14, initially kept quiet but later abused drink and drugs and attempted suicide three times.
The offence came to light after the victim was talking to a social worker about her history of behavioural problems at school.
Judge Lord Woolman called for background reports and remanded Scougal in custody pending sentence next month.