Osaka also converted four break points and won 63.2 percent of Kerber's second serves-again, a sign of her dominance.
The German was still ranked No. 1 in the world as recently as July, but will slip significantly from her current ranking of sixth after the U.S. Open is completed, having become only the second defending women's champion to lose in round one.
"She's a very aggressive player, but I knew this before".
"But I believe if I play good tennis, I have a good chance to stay there".
Also in action are 2004 champion Svetlana Kuznetsova, who meets Marketa Vondrousova of the Czech Republic, and French Open victor Jelena Ostapenko, up against Lara Arruabarrena of Spain.
Yet, Osaka felt nervous against Kerber in the 23,771-seat Arthur Ashe Stadium, having lost to American Madison Keys in the third round of the U.S. Open a year ago after leading 5-1 in the third set.
The Japanese-American is a fearless ball-striker and Kerber had no answer, netting a final forehand to succumb meekly after just 65 minutes.
It was Osaka's first victory over a top-10 opponent after she was oh-so-close to beating a top player here past year, blowing a 5-1 lead in the third set and losing to Madison Keys in the third round. "I did that today and so I want to carry that into the next match", added the Japanese teenager, who secured her first career win over a top-10 player. "When it was 4-1, I was walking here thinking, 'I really hope I don't do what I did here previous year'". "But at the end, I know that I'm strong and I know that I will come back stronger, for sure". I know that I will not give up like this.
Harvey sends floodwaters into Texas nursing home, 15 seniors rescued
McIntosh later spoke to ABC News , and said he is very grateful for the people involved in the rescue. McIntosh's wife told the newspaper they were hoping authorities would see it and come to get them.
The second raced by in even more impressive fashion, as the 19-year-old cranked up her winners to 22 compared with just nine to Kerber.
"This court hasn't really been a fond memory, but now I hope I overlap that", Osaka said in a television interview after.
"So the site feels really familiar to me". I just tried to focus on what I could do to win the match.
Osaka lost to Madison Keys previous year but had led 5-1 in the final set before her nerve failed.
The Czech defeated Poland's Magda Linette 6-2 6-1, and was relieved to safely negotiate the first hurdle. It was a little bit hard, but I think I made it pretty okay today.
The madness continued on Tuesday, August 29, when defending champion Angelique Kerber lost to one of the future stars of the WTA tour.
"It was a little bit hard, but I think I made it pretty okay today".
The game could be better.
- German Nurse May Have Killed 84 Patients, Authorities Say
- Mauricio Pochettino points to lack of concentration for Wembley struggles
- Berkeley Police Arrest 13 as Anarchists Storm Right-Wing Event
- Lyon in rare company with 250 Test scalps
- Slowest US box office in 15 years
- United Kingdom officials in Brussels to resume Brexit talks
- JDU to seek Sharad Yadav's disqualification from Rajya Sabha
- Android 8 Oreo update for HTC 10, U11 and U Ultra confirmed
- Minnesota volunteers join Harvey relief effort
- Lebanon: Remains of Soliders Missing from 2014 Found