Authorities in Tokyo confirmed 772 fresh cases of novel coronavirus infection on May 15, of which 234, or about 30 percent, involved those in their 20s.
The daily average of new cases for the week ending May 15 came to 876.4, up 12.9 percent over the previous week, according to metropolitan government officials.
Among the latest patients, 135 were in their 30s, 125 in their 40s and 97 in their 50s.
Patients aged 65 and older accounted for 77 cases.
Eighty-five patients, up by one from the previous day, displayed serious symptoms that require ventilators, or an extracorporeal membrane oxygenation (ECMO) device, which circulates blood through an artificial lung.