The daily number of new COVID-19 cases hit 251,626 nationwide as of 6 p.m. on Aug. 18, topping the previous high of 250,347 marked on Aug. 10.
At least 21 prefectures reported single-day records as of 6:30 p.m.
Of the 251,626 cases, 27,453 were confirmed in Tokyo, followed by 24,323 in Osaka Prefecture.
Tokyo’s latest tally was down 3,794 from a week ago, marking the third straight day of a week-on-week decline.
The 27,453 new cases include 2,024 cases where samples were brought in from outside the capital for testing or positive test results were registered at centers outside Tokyo.
Officials also reported the deaths of 27 patients in their 60s to 90s in the capital.
The daily average of new cases over the week through Aug. 18 in Tokyo was 24,347, or 82.1 percent of the average for the preceding week.
People in their 20s represented the largest age group of new patients, at 5,067, followed by 4,851 in their 40s, 4,781 in their 30s and 3,867 in their 50s.
Additionally, 2,898 people aged 65 or older tested positive.
The occupancy rate of hospital beds for COVID-19 patients in Tokyo was 59.8 percent, while 33.8 percent of hospital beds for severely ill patients were filled, officials said.
The Tokyo metropolitan government said it would consider asking the central government to issue a state of emergency for the capital if the occupancy rate of beds for seriously ill patients was between 30 and 40 percent.
The metropolitan government defines seriously ill patients as those requiring ventilators or ECMO heart-lung bypass machines.
Their number dropped by two from the previous day to 33 on Aug. 18.