Covid wasn't mentioned.
It was heavily implied. It's the closest you can get to saying covid without actually saying the name.
i remember that one bl manga with the timeline thing and the mc realised the difference bc covid hadn't happened yet in ml's timeline LMAO
He mentioned an epidemic. Japan suffers every year from heavy influenza epidemics with people getting seriously ill and dying.
always getting a whiplash whenver there's covid mention in manga