More details on what really went down between Harry Styles and rumored girlfriend Nadine Leopold at the former's star-studded 21st birthday bash have been revealed.

The Sun (via Mirror) previously reported that the Victoria's Secret model made the One Direction member's recent party special.

"Everyone's teasing him, saying he's in love, and he's not denying it. It's the real deal," an insider said. "He's never felt this way about anyone before. Harry has spent virtually all his free time in Los Angeles with Nadine. They're infatuated with each other and can't stand being apart... there's nobody else he'd rather be with on his birthday."

According to Heat magazine (via Sugarscape), the pair was spotted making out.

"Cara Delevingne, Kelly Osbourne, Kendall Jenner and Alexa Chung all arrived together, and Adele and James Corden also showed up," an insider revealed. "Everyone from David Beckham to Cindy Crawford was there -- Chris Martin and Jennifer Lawrence were doing shots at the bar."

Styles and Leopold were seen "kissing and holding hands -- despite three of his exes also attending: Kimberly Stewart, Cara and Kendall."

The latest report follows The Daily Star claiming that the "Steal My Girl" crooner even added the initials of his love interest to his extensive body art collection to celebrate the big 21.

"Harry made everyone sign confidentiality agreements so the girl's letters are a secret at the moment," a source close to Shamrock Tattoo Company revealed. "But he had two sets of initials together -- 'HS' is one of them of course, but everyone's saying that the other initials are 'NL' -- for Nadine Leopold."

Also, he allegedly requested the tattooist come to his house in order to keep the inking process private.

"Harry used to go to tattoo parlors when he came to LA," the source added. "But he gets mobbed so much that he has an artist go to his house instead."