Naomi Osaka was sensationally accused of unsporting behaviour and offered an ice-cold handshake by Sorana Cirstea after beating the Romanian star 6-3, 4-6, 6-2.

The former Australian Open champion was visibly surprised by the curtness of Cirstea's response to the offer of a handshake after their lengthy battle on Margaret Court Arena.

The former World No 1 asked: 'What was that for?'

'That?' Cirstea responded as she made her way towards the umpire. 'For not knowing what fair play is, my friend.

'You're playing for so long and you don't know what fair play is?' 

The 35-year-old swiftly left the court, leaving Osaka to mull over her reaction as she awaited her on-court interview. 

Asked about the reason behind Cirstea's reaction, Osaka brushed off her opponent's accusation.

'Apparently a lot of "come ons" that [she] was angry about, but whatever,' said Osaka, before making a dramatic shrugging gesture. 

'She's a great player, I think this was her last Australian Open, but... sorry she was mad about it.' Those comments prompted a round of shocked laughter from fans. 

Cirstea, who reached a career-high ranking of world number 21 in 2013 and will retire at the end of this year, allowed her frustrations to bubble over deep into the third set, after accusing Osaka of disrupting her service game. 

At 30-all and already 4-2 down in the decider, Cirstea faulted on her first serve and, as she recovered, a voice which she believed to be Osaka's was heard saying 'Come on' from the other side of the court. 

Stopping play, Cirstea took her concerns to the umpire, asking: 'Is that okay? To do "come on" between points?'

'Between serves, you haven't got the ball in your hand, so it's okay,' the umpire replied. 

'So it's OK? I can talk between (serves)? I can go "Come on", and talk?' Cirstea queried. 

'You're not serving yet, so it's not a hindrance,' the umpire explained. 'If you're in the service motion, no.' 

Cirstea explained that it was not the first time that she had an issue with Osaka but eventually returned to work on her second serve.

When asked to elaborate on the incident in her post-match press conference, Osaka remained unperturbed by the whole episode.

'I just thought, "Huh, that's interesting",' she said. 'For me, no one has ever complained about it before. And also the umpire didn't tell me I was wrong, I was like "Oh, OK". 

'I thought we moved past it'. 

Cirstea was also keen to move on by the time she faced the press, saying she had no issue and was not keen to focus on the incident after her final appearance in Melbourne. 

'If I'm being honest, I've never been involved in something like this,' added Osaka when asked if she planned to discuss the issue again with Cirstea. 'I don't know if we're supposed to leave it on the court.

'I'm a little confused, but I get that emotions were very high for her, and I also want to apologise to her. The first couple of things I said on the court (in my interview) were disrespectful and I don't like disrespecting people, it's not what I do.

'If she wants to talk about it, then yes. But, when I'm pumping myself up in my head, it's purely for me.' 

On explaining why she had ramped up the volume of her 'Come ons' after Cirstea spoke to the umpire, Osaka continued: 'I'm not someone who likes to be casually disrespected, so I probably overdid it the next couple of points.

'But it takes a lot out of me. I'm very tired now.' 

16th-seed Osaka has not moved quietly since her arrival Down Under, capturing international headlines ahead of her first round match with a dramatic on-court entrance in a couture outfit by London-based designer Robert Wun. 

The four-time Grand Slam champion paired her custom Nike kit with a veiled hat featuring a butterfly, flowing white trousers and a white umbrella in what she described as a jellyfish-inspired outfit. 

Osaka lost the hat and the umbrella for her return to action on Thursday evening, but continued to sport her unique look, which she described to US Vogue as having stemmed from reading a story to her two-year-old daughter, Shai. 

'There was an image of a jellyfish, and when I showed it to her she got so excited,' Osaka explained, before fleshing out the concept with the design team at Nike and reaching out to tennis fan Wun. 

After securing her spot in the third round, Osaka admitted that she was unwilling to reveal whether she would be changing up her look yet again for her meeting with home favourite Maddison Inglis. 

Instead, Osaka claimed she was keen to give fans 'a reason to watch' by keeping her next fashion statement under wraps.