She told the Sunday Mirror they met up once a week at the height of the affair and said “I loved him, I adored him.”
Ms Arcuri, 35, said they had a mutual “physical and intellectual attraction”.
They shared a love of Shakespeare and she codenamed him Alexander the Great, a nod to his real first name Alexander.
She told the paper Mr Johnson loved her body and mind and “couldn’t keep his hands off me” on their first liaison.
Ms Arcuri said that the romance spanned from 2012 to 2016 during Mr Johnson’s second term as London Mayor when he was still married to ex wife Marina.
It was later revealed that Ms Arcuri was invited on taxpayer-funded foreign trade trips led by the then-mayor, sparking a political storm.
He spoke at a series of technology events organised by Ms Arcuri, who went on to receive £126,000 of taxpayer money in event sponsorships and grants. The bulk, £100,000, came in a government grant in 2019.
She maintains she was invited on trade trips in her own right as a member of the London tech-scene “ecosystem”.
An investigation into the trips cleared Mr Johnson, 56, of any wrongdoing when claims of the affair first emerged.
Ms Arcuri said that she considered him a “cowardly wet noodle” for not standing by her when the row broke out.
She added: “We were in an intimate relationship for four years. I loved him, and with good cause. But the man I thought I knew doesn’t exist any more.”
Ms Arcuri claimed they first had sex in her Shoreditch flat hours before Mr Johnson sat between Marina and Princess Anne at the opening of the 2012 London Paralympics.
She revealed that he had to hunt for a stray sock before heading off to the event.
She also claimed he had to borrow £3.10 on their first date and later shrugged off concerns about kissing in public, saying: “This is my city, I don’t care.”
Ms Arcuri said Mr Johnson wined and dined her openly at a London restaurant, telling her: “I want to date you, you’re the only American I’ve ever fancied.”
He requested racy images of her and said one raunchy picture was “enough to make a bishop kick a hole in a stained-glass window”.
Ms Arcuri was a business student when she met Mr Johnson when he was speaking at an event in 2011.
She said: “He entered the room, his hair all dishevelled. That’s when I saw the first real magic of Boris Johnson.
“He’d turn the whole room into a bunch of howling schoolgirls. I made a beeline for the front of the line. I said, ‘Hello, my name is Jennifer, if you didn’t know me, now you do’.”