The girl, who is from the Ruapehu region, told the court the man who attacked her was a Mongrel Mob member, with short black hair, tattoos, a scar on his abdomen and he had anger issues.
The offender got into bed with her on May 9 and began touching her inner thigh before removing her onesie and underwear and sexually assaulting her, the court heard.
"I asked him what he was doing and he told me to shut up.
"He touched me in places I didn't want him to and he raped me."
She said the man, who had a girlfriend and a son, put his pants back on after the sexual assault but threatened her before leaving.
"He said don't tell anyone or else, or I will hurt you or something like that.
"I just froze up."
Afterwards the girl said she went to the bathroom and took a shower before returning to bed.
She didn't tell anyone about how happened until weeks later when she confided in the school nurse.
Crown prosecutor Josh Harvey described Herewini's actions as criminal behaviour.
Harvey said five witnesses would be called during the trial which was expected to take three to four days.
Lawyer Steve Winter said the defence position was simple; Herewini was not guilty and there were contradictory accounts about what happened on the night.
"These things did not happen and he didn't do it," Winter told the court.
He urged the jury to put aside any feelings or prejudice and sympathy and focus on deciding the case on the evidence presented in court.
Where to get help:
• NZ Police
• Victim Support: 0800 842 846
• Rape Crisis: 0800 88 33 00
Rape Prevention Education
• Empowerment Trust
• HELP: Call 24/7 (Auckland): 09 623 1700, (Wellington): 04 801 6655
• Safe to talk: a 24/7 confidential helpline for survivors, support people and those with harmful sexual behaviour: 0800 044334.
• Mosaic - Tiaki Tangata Peer support for males who have experienced trauma and sexual abuse: 0800 94 22 94
• If it is an emergency and you feel like you or someone else is at risk, call 111.
