The girl sent him pictures of her genitals and other body parts.
On his encouragement, the victim agreed to meet with him, and asked him to bring her alcohol. The pair drove around until they found a place to park, and the victim performed a sexual act on him.
Afterwards, he gave her a Pump water bottle filled with alcohol, and dropped her back home.
According to the victim impact statement, the girl said the offending had a significant impact on her, "knocked her confidence" and created a difficulty for her to trust others or get into relationships with boys her age, Judge Hobbs said.
"She was trying to be a grown up, but that has obviously had significant negative consequences for her."
However, the girl did not want the offending to define her, and wanted to move on with her life.
While defence lawyer Elizabeth Hall acknowledged the vulnerability of the victim due to her age, she said it was not entirely a case of a naive and unsophisticated young person being offending against.
"I accept that the victim has voluntarily engaged in discussion with you of a relatively graphic [nature]," Judge Hobbs said.
However, while the sexual activity might have been consensual, it was not consensual in the sense that the victim was old enough to give fully informed and lawful consent, he said.
Hall said it was important to "keep a very firm grip on what actually happened here".
"Was there an intention by [my client] to meet up and have casual sex through the internet? Absolutely."
However, she said, the offending was not some type of paedophilic attraction.
"This is a man who had everything. He had a supportive partner, a home, excellent job, a career path, and the stress of all of that caused him to go on to the internet and look for the immediate, quick release of anonymous sex."
He was now working to understand how his life got "so out of control", Hall said.
"For him, the conviction is the most devastating thing that is going to come out of this."
Judge Hobbs said the Crown viewed the offending and "grooming or manipulation".
"Clearly this has been a significant fall from grace," he said.
He sentenced the man to nine months of home detention.