A man says he told his abuser that if he touched his brother he would "end him".
The man, now aged in his 40s, is giving evidence in a closed courtroom at the High Court in Auckland where Alosio Taimo, 55, is on trial for sexually abusing 18 boys over 29 years.
Mr Taimo - a former junior rugby coach and a teacher aide - has denied 83 sex offences.
The man said Mr Taimo was a family friend and forced him to touch him at night.
He recalled both incidents happening about six months apart and he cried himself to sleep afterwards.
The man said he was just a boy at the time. He felt helpless at the time and the experience left him shocked.
"You can't really help the kind of sickness people have - it's the way of the world."
He said his school days were happy and he had some close friends that he spent time with.
"That was the good times. It was only at night when you're by yourself - that's when the darkness happens."
He said years after the abuse he met up with Mr Taimo.
"[I said] if he ever touched my little brother, I was going to end him."
He said Mr Taimo did not respond.
The man said he told his long-term partner about the abuse and they are still together.
The man said he read about Mr Taimo's charges in the media last year and approached police.
Under cross-examination from Mr Taimo's lawyer, Panama Le'au'anae, the man confirmed he hadn't told anyone about the abuse at the time.
"I was too scared of 'Sio [Mr Taimo] ... He might give me a hiding or something."
He confirmed he may have got the dates of the events wrong, but he was having to dredge up over suppressed memory from more than 20 years ago and the incidents did happen.
Mr Le'au'anae asked if he had been taught about "good touching and bad touching" at school.
The man replied: "Back then, there was no such thing as good touching or bad touching - the only thing [that was taught] was religious teaching."
When Mr Le'au'anae accused him of making up his evidence, the man responded: "I'm just here to tell the truth."
"You can stand there and say that it didn't happen but in my heart of hearts, I know it did happen."
The trial, before Justice Moore and a jury, is in its fourth week of 10.