A Launceston man gave a then 15-year-old girl two grams of cannabis after they had sex in his car, a Supreme Court jury heard.
The man, now 44, pleaded not guilty to three counts of penetrative sexual abuse of a young person between June 1 and July 31, 2018.
Crown prosecutor Tamila Smith said the charges arose from one incident.
She said the girl met the man who provided her with cannabis in early 2018.
"Sometimes she paid and sometimes she paid in other ways," Ms Smith said.
The woman gave evidence that she sent the man a picture of her breasts hoping that would be the end of it but he persisted.
Ms Smith said in June 2018 she met him and they drove to a cul-de-sac and she had oral sex with him, he had oral sex with her and they had sexual intercourse with a condom.
The complainant said he later contacted her to find out if she was pregnant and whether she had told anyone.
She said she blocked him on Facebook and only had contact a few more times to purchase cannabis.
She sent the man's son a screenshot of a text message from the accused man. The message said the man wanted to have sex with her.
The man's partner wept and the trial briefly halted as she gave evidence that the girl texted messages to her 17-year-old son "gloating" that she had had sex with his father. Ms Smith asked whether she went to police.
"No, not straight away," she said. "I did after I was assaulted by [the man's partner] in 2018."
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Under cross examination by defence counsel Lucy Flanagan, the woman said she had backdated her birth date on her Facebook profile in 2012.
The woman said she remembered a conversation in which the man said he was going to buy a large amount of cannabis.
"Did [he] suggest you could have any amount for free?" Ms Flanagan asked. "Yes," the woman said.
"Did you contact him at 3am and say you were ready to see him and that is when he collected you at home?" she asked. "Yes," she said.
The man's partner gave evidence that the man told her during an argument that the girl was 16 years old at the time.
Under questioning from Ms Smith, the man's partner said she sent the girl text messages pretending to be the man because he had never told her specifically what happened in the car. She admitted she assaulted the girl in November 2018.
She denied a suggestion that she was lying to the court because she was still in a relationship with him.
"Why would I protect him this is my perfect revenge time," she said.
As she left the court she said "I love you honey, I love you."
The trial before Acting Justice David Porter continues on Tuesday.