"I love you, Serena," he added before adding "I love you, mom, I love everyone."
Osaka, the twentieth seed, has faced and defeated Serena once, in Miami in March.
That victory came just a week after he lifted his first high-level trophy at the prestigious Indian Wells event in California.
Saturday will be the fulfillment of Osaka's childhood dream of facing Serena in a Grand Slam final.
"He still feels a bit surreal, even when I was a little boy, I always dreamed that I would play against Serena in a Grand Slam final," he said.
"Just because it's happening, I'm very happy." At the same time, I feel that although I should enjoy this moment, I should still think of him as another party.
"Yes, I really should not think of her as my idol, I should try to interpret her as an opponent."
The contrast of the Sabbath can not be greater.
Serena will play in her 31st Grand Slam final and ninth in the US Open, where she is six times champion.
When the American, 16 years older than her, won her first US Open in 1999, Osaka was not yet two years old.
Whatever happens in the final, Osaka said she will remain a fan of the American who is chasing a major 24th major, just a year after giving birth and undergoing four postnatal surgeries.
"When you come back and then go to the final of two cars, I think it's really amazing," Osaka added in reference to Serena's job at Wimbledon in July.
"I'm sure everyone knows that Serena is really good, of course, but I do not want to think too much about this game, so I'm not going to think she's much better than her in Miami.
"I'm going to go out and play, as I know she's a good player, I do not want to be surprised if she plays better or not."
Keys had beaten Osaka three times out of three before the semifinal on Thursday, but the 14th seed admitted that he had been completely overtaken in the semi-final.
"I thought I could take a break, but every time I hit an ace or a big shot," said the 23-year-old who accumulated 13 break points that were all saved by the Japanese star.
"It was difficult, you think it's going to stop but she does not, it was very impressive."