Craig Fletcher also monitored the youngster’s every move and threatened extreme violence against male friends, forcing her into thoughts of suicide, Leeds Crown Court was told.
The 40-year-old was sentenced today when it was heard that Fletcher developed a obsession with the teenager when she was just 14 and he began trying to control her.
On one occasion he went to a McDonald’s and threatened to break a boy’s legs if he went near her, and pursued another in his car.
Prosecuting Thomas Storey told the court how, through his technical know-how, Fletcher was able to get access to her Facebook and Twitter accounts.
He even bought separate mobile phones to avoid being detected and used different IP addresses to cover his tracks.
As the girl grew older, she found a boyfriend but they both began receiving text sexually explicit messages sent by Fletcher, claiming they had each been unfaithful to one another in an attempt to ‘drive a wedge between them’.
Having hacked their accounts, Fletcher then sent separate private photos of the girl and boy to their friends.
When suspicions were aroused, he was arrested in September 2017 and denied any involvement.
His computer was later seized where there was a large number of extreme pornographic images, including animals, sadism and mutilation.
He eventually admitted two counts of stalking, four counts of sending private photographs without consent and having extreme pornography.
Mr Storey told how the ordeal had hugely affected both the boy and girl, with both admitting to thoughts of suicide.
They had both struggled with trust issues since, and both failed to get the grades they were expecting at school.
Mitigating, Matthew Harding, read a letter from Fletcher out in court in which he apologised for his actions, saying he was ‘disgusted’ with himself and had ‘lost everything’.
On sentencing Fletcher, Judge Christopher Batty said: “You have never provided an explanation as to why you did this, but I take the view it was born out of obsession and nothing else.
“Your campaign caused significant stress to two young people. You were able to stop this any time but you did not.
“You are now ashamed of what you did but you only have yourself to blame. This was not a one-off matter, it was a long course of action exacted over many months.
“There was a high degree of planning and sophistication intended to maximise distress. The harm you caused is most serious.”
On top of the jail sentence, Fletcher, now of Bordeaux Road, Stoke-on-Trent, was given a lifelong restraining order and told never to return to the Wakefield area.