The offending occurred on June 3 this year and came to light when she told her mother and they went to police.
He admitted the offending in two video interviews with police and later pleaded guilty in court.
Two background reports were presented to the court today to assist with sentencing, including a psychological assessment.
"You understand the enormity of what you've done here; the damage you have done to this child and to the rest of the family," Judge Thomas Ingram said, acknowledging that Richards was shown to demonstrate remorse.
"You've accepted you've done wrong - as you should."
The severity of the offending was exacerbated, however, due to the child's age and vulnerability.
The judge began with a sentence starting point of 10 years' imprisonment, with a 25 per cent discount for an early guilty plea and a further 15 per cent discount for remorse and previous good character.
Richards was sentenced to six years' imprisonment, and will be added to the child sex offender register.
SEXUAL HARM - DO YOU NEED HELP?
If it's an emergency and you feel that you or someone else is at risk, call 111.
If you've ever experienced sexual assault or abuse and need to talk to someone contact the Safe to Talk confidential crisis helpline on:
• Text 4334 and they will respond
• Email support@safetotalk.nz
• Visit https://safetotalk.nz/contact-us/ for an online chat
Alternatively contact your local police station - click here for a list.
If you have been abused, remember it’s not your fault.
