As a successful mind coach, Sean Patrick Lynch worked with the likes of former world No.1 golfer Jason Day.
But Lynch also used his skills to groom a gifted young golfer, Brisbane District Court has heard.
Lynch, 68, was dubbed "king of the kids" working as a golf mentor in Queensland.
As a mind coach, however, the court heard Lynch was also able to manipulate a girl into starting a "secret relationship" and convincing her not to share it with anyone - including her family.
"He is a successful mind coach (with) Jason Day, all these people we have heard about," crown prosecutor Chris Cook told the jury during the two-week trial.
"He was able to manipulate the mind of (the girl) not to tell her family any of it.
"She didn't say anything because she trusted that everything that Mr Lynch did was in her best interests."
During one alleged incident Lynch told her that "he was happy for it to stop but that it would help her golf so much".
Lynch was accused of gaining the girl's trust before engaging in multiple indecent acts from April 2017 until December 2019.
Lynch exchanged text messages and phone calls with the girl, progressing to "dirty talk" and showing her pornography, Mr Cook said.
At times she would even stay at his Brisbane home with his family in a spare room downstairs.
A string of texts between Lynch and the girl were shown in court.
In one exchange the girl described something as "just beautiful" and Lynch responded "like yourself".
When asked if this was an example of his grooming, Lynch described it as a "normal response".
"To a 13-year-old girl?" Mr Cook asked.
"Yeah, in my world," Lynch replied.
The girl described Lynch as "sexy" in another text.
"You didn't tell her at any stage this is an inappropriate chat between a 60-something-year-old man and a 13-year-old child?" Mr Cook asked.
"No," Lynch said.
The girl finally went to the police in December 2019 after tearfully confiding in her family.
"She was bawling her eyes out," the girl's grandfather told the court.
"She did say ... Sean had made her say it was her fault and that's why she was scared to come and tell her family."
She rang Lynch after speaking to police who recorded the phone conversation.
An excerpt of the call was played to the jury in which the girl asked whether Lynch could remember one of the indecent acts.
"We didn't go too far with that. I was weak ... all that's happened, can we just forget all that stuff," Lynch said.
The girl tearfully responded: "But I can't."
Lynch pleaded not guilty to 11 charges.
The jury, which began deliberations on Thursday morning, found Lynch guilty on five counts of indecent treatment of a child under 16 under care.
He was also found guilty of grooming and one count of indecent treatment of a child under 16.
Four of the guilty verdicts were by majority after the jury was sent back for further deliberations late Friday afternoon.
However, Lynch was found not guilty of possessing child exploitation material as well as another three counts of indecent treatment of a child under 16.
He will be sentenced by Judge Vicki Loury in November.