From one point of view, it is a remarkable success story. In 2000 Japan had 4.7 million foreign tourists a year. The government of the former prime minister Shinzo Abe set an ambitious goal of 20 million foreign visitors a year by 2020, and achieved it five years ahead of schedule.

After a pandemic slump, the foreign tourists are back in force: the Japan Travel Bureau, a travel agency, estimates that there will be more than 33 million foreign visitors this year, an all-time record, fuelled partly by the weak yen, which makes Japan remarkably cheap for those spending foreign currency.

The speed and volume of the surge has brought prosperity to tourist businesses large and small, including the one run by Sherlock; as many as 30 visitors a day were paying 6,000 yen (£30) each for his walking tours. But the sheer number of visitors has overwhelmed many places.