It all started with a tweet: after asking for suggestions from fans, two-time Grand Slam champion Naomi Osaka has been sharpening her interview skills during tennis' hiatus — but as the interviewer rather than interviewee.

The former World No.1 hosted Q&A sessions on Instagram live in recent days, and after ATP stars Frances Tiafoe, Gael Monfils and Stefanos Tsitsipas were first up, Osaka linked up with teenage sensation Iga Swiatek on Sunday to discuss the origins of their friendship.  

Osaka and Swiatek revisited how they first struck up a bond during last summer's North American swing, after they faced off for the first time in the third round of the Rogers Cup in Toronto.

Following a thrilling match, complete with social media banter, they later practiced together at the US Open. 

"Toronto was special for me because usually when I was playing in big stadiums, I got so stressed that I couldn't play," Swiatek said. "That happened against Simona in the fourth round at the French Open.

"When I was playing Caroline [Wozniacki] the round before our match, I was losing 6-1, and I won [1-6, 6-3, 6-4]. That was amazing for me because I finally knew what to do to win in big stadiums.

"When we were playing against each other, I was excited for the whole match. That was the first match I lost, where I wasn't even mad after."

Later on in Sunday's chat, the two revealed that they actually first crossed paths during the grass court season. 

Related: Starstruck Swiatek on Osaka practice: 'I'm new here, I'm not used to talking to celebrities'

"I first saw you in Birmingham... and I felt like you were just staring at me. I was like, 'Why are you staring at me? Did I do something wrong?'," Osaka recalled.

"Creepy," Swiatek retorted. 

"But in Toronto, I was like, 'Oh, actually, she's very nice!', and I was surprised because I thought you hated me or something... so the entire time, I was like, 'Oh, no!'"

"I always thought you were very interesting, and you were playing very well and I wanted to observe was you were doing, just to be better," the Polish No.2 continued.

"I remember we were stretching next to each other in Birmingham and I saw an Instagram that you posted for your dad's birthday... and I wanted to talk to you about that and tell you that it was funny, but I was too shy, so I just kept stretching."

In addition, the soon-to-be 19-year-old — who will celebrate her birthday next week — revealed that she didn't grow up watching too much tennis or idolizing a specific player.

Read more: Osaka and Venus twist and dish in live workout session

Instead, her love for the sport deepened when she was already an elite player on the junior circuit. 

"It's weird, because I wasn't even watching tennis when I was little," Swiatek said. "When I got home after school and practices, I was so tired of tennis and I was asking why my parents were event watching because I had enough tennis on court. 

"When I went to my first junior Grand Slam at the French Open, I realized that tennis is greater than I thought and I fell in love. I was watching Rafa [Nadal] a lot because I love to play on clay, and it's Rafa, right?"

Playing the role of interviewer, Osaka also grilled Swiatek on some of her favorite foods — which include watermelon, salmon and sushi, and the Italian dessert tiramisu — and how she juggles the demands of being a professional athlete and student simultaneously, while both talked about what they'd like to be known for away from the court.

"This is really serious!" Swiatek joked, while adding, "I was to be open-minded about things, and learn new stuff. I would like to develop not only in sports... it would be nice if I went to university after I finished, or maybe do online in a few years, just to know more about the world." 

Tennis United Episode 7