Naufahu rose to fame starring as Sam the ambulance officer in the original cast of Shortland Street before moving on to act in the Power Rangers television series.
He returned to Shortland Street in 2014 for four months. He also reprised the role for an episode in October 2014.
In 2006, he won best supporting actor for the film No.2 at the Air New Zealand Screen Awards.
The offending took place between 2011 to 2013 in Naufahu's Auckland acting classes.
During one of the classes, Naufahu's "kissing became more passionate and the touching became more invasive".
One of actresses said she had "no lust or love" for Naufahu but simply saw him as her "acting coach".
Naufahu told her she was amazing and "had been turned on by the exercise".
But she said she had "felt so uncomfortable and intimidated".
Judge Thomas said Naufahu "caused an enormous amount of harm to six very vulnerable women".
He said it wasn't the extent of touching but the extent of a breach of trust.
Naufahu will be sentenced in November.
He told the Herald: "I accept now that I made errors and crossed boundaries that should not have been crossed. The Crown is abandoning the other, more serious, charges that were initially alleged and which I simply rejected as they had no credible foundation. It is a relief to me that this now brings closure.
"I am pleased this case has resolved as this period in my life has been very hard for me and my family. There has been a lot to confront and resolve. We have done that. I am sure it has also been hard for those students who became involved on both sides.
"I hope that by acknowledging the accepted inappropriate conduct, this now stops and everyone can move on."
Naufahu said he had "only ever wanted to help actors, to inspire and challenge them, like I was".
"I have only ever wanted to provide opportunities, where they may not have otherwise existed. I have never sought to offend or upset any one. Yet I accept that I have and this has been hard to confront."
He said he cared about the acting profession and wanted to promote it: "I have been passionate, clearly too passionate. Passion sometimes confuses boundaries and emotions. I see that now."
"If I have hurt these students and let them down, I regret that. That was never my intention."
Naufahu apologised to the women involved and said he accepted he had let himself and his family down.
"I see now that I became that guy, that I myself did not like seeing in others and sought over years to protect others from. That horrifies and saddens me."
He concluded: "I am of course ashamed and disappointed that my conduct has led to this. I never saw this for myself or for the others so affected. However, I will learn from it and ensure that I grow from it and that no other female actor is placed in this position again.
"To those hurt and upset by my conduct, I am sincerely sorry.
"To my fans and supporters, I am sincerely sorry."
