Tyrin Hamuera Tutaki (21) was a "leading light" in his community, his counsel Brian Kilkelly said.
"Tutaki was a trusted member of the community and was seen by many children as a role model due to his heavy involvement in Maori health and education programmes which targeted youth," police said.
As a teenager he addressed large gatherings on suicide prevention.
But he was harbouring a secret, the exposure of which led him to his own thoughts of self-harm.
Through his community roles, Tutaki met an 11-year-old in 2014 and began mentoring him.
Over the ensuing months, the defendant developed strong feelings for the boy, a police summary said.
"At the beginning of 2016 the friendship spilled over into a physical relationship, shortly after the victim’s 13th birthday," it said.
The pair had regular contact and progressed from kissing to performing sex acts on one another.
In mid-June others began to notice their close bond and Tutaki decided their private contact should cease.
But a year later, they bumped into each other at a marae event.
An evening walk became a secret sexual liaison and the rendezvous was repeated a week later.
That was the last time Tutaki offended against the boy, who was then 13.
The Dunedin District Court previously heard how the duo would meet in "discreet public places" to engage in the illicit acts.
These included a rugby club, a primary school and the victim’s home.
When spoken to by police, Tutaki said "their friendship had become a relationship where they both loved each other. Although he knew it was wrong, he felt confused and was unable to control the direction of the relationship when it became sexual".
Mr Kilkelly said his client was fully aware of the gravity of his offending and was strongly motivated to address his issues so he would remain safe in the future.
"He has fully participated in describing and exploring his behaviours and thinking about offending," Mr Kilkelly said.
He told the court Tutaki’s work as a cultural orator, advocate for young people and emergency services volunteer would go on hold "for a significant time".
"His fall from grace has been huge."
Judge John Macdonald sentenced Tutaki to nine months’ home detention and 200 hours’ community work.
The defendant was added to the Child Sex Offender Register.
