Keiko Kawano's company, Egaoiku, has seen a more than four-fold jump in demand for smile instruction since last year.

A one hour-long session costs 7,700 yen (£44.24), and customers range from companies investing in salespeople to local governments supporting residents' wellbeing.

Himawari Yoshida, 20, one of the students taking the class as part of her school's courses to prepare them for the job market, says she needed to work on her smile.

'I hadn't used my facial muscles much during COVID so it's good exercise,' she said.

Even before the pandemic, donning a mask in Japan was normal for many during hay fever season and around exams due to concern about getting ill for a key life event.

But while the government may have lifted its recommendation to wear masks in March, many people have still not let them go on a daily basis.