The defending champion consoled 15-year-old American Coco Gauff after beating her 6-3 6-0 in the third round of the US Open.
"She was crying, she won. I was crying. Everybody was crying!" said Gauff. "I didn't know why she was crying. I was like, 'you won the match!'"
It was not the first time Osaka has shown compassion in victory and after a heart-warming embrace at the net, she invited a tearful Gauff to speak to the crowd in a post-match interview.
"I was wanting to leave the court because I'm not the type of person who wants to cry in front of everyone. I didn't want to take that moment away from her, as well," said Gauff, competing in only her second Grand Slam singles main draw.
"She told me it's better than crying in the shower. She convinced me multiple times to stay. I kept saying no. Finally I said, OK, I'll do it. Because I didn't know what to do.
"I'm happy that she kind of convinced me to do it because, I mean, I'm not used to crying in front of everyone."
Osaka, 21, was holding back tears herself when she then spoke directly to Gauff's box, before apologising for playing so well.
Naomi Osaka celebrating after progressing to the quater-final stage of the US Open
"You guys raised an amazing player," said the Japanese world number one. "I used to see you guys training in the same place as us. The both of us made it and are working as hard as we can. I think this is the most focused I have been since Australia.
Turning back to Gauff, she added: "I am sorry for playing you in this mentality. It was super fun!"
Osaka later told a news conference: "It was kind of instinctive because when I shook her hand, I saw that she was kind of tearing up a little. Then it reminded me how young she was.
"I was just thinking it would be nice for her to address the people that came and watched her play. They were cheering for her."
Gauff said she had not expected that reaction from Osaka.
"I'm glad that I was able to experience that moment," she said. "I'm glad the crowd was kind of helping me and her.
"For me a definition of an athlete is someone who treats you as their worst enemy on the court but after they treat you like you're their best friend. That's what she did."