The Tokyo metropolitan government confirmed on Sunday 4,392 new coronavirus cases, marking the highest figure ever reported for that day of the week.
The number, which surpasses the 4,295 cases reported last Sunday, was down from the 5,074 new cases the previous day, when they topped the 5,000 level for the fourth straight day.
Nationwide, the number of new infections totaled 22,285, dropping below the 25,000 mark for the first time in four days.
Tokyo's seven-day rolling average of COVID-19 infections stands at 4,732.9 per day, up 11 percent from the previous week, according to the metropolitan government.
Outside the capital, 2,524 new cases were confirmed in Kanagawa Prefecture, 2,221 in Osaka Prefecture and 1,696 in Saitama Prefecture.
The number of COVID-19 patients with severe symptoms rose to 1,891 cases across the country, up three from Saturday and hitting record highs for the 10th straight day.
Despite anti-virus measures taken under the state of emergency and quasi-emergency status in hard-hit areas, Japan is grappling with its largest wave of infections yet, with the strain on the medical system showing no signs of abating.