May be one of the major things which you did not see in Europe before the Corona virus crisis. Wearing face mask was very common in Japan before the crisis.
Actually there were three types of persons to wear the face masks in Japan.
1) Prevent not to spread airborne diseases to others. Which means that the person wearing the mask is ill - has a cough/flu.
2) Prevent not to get airborne diseases from others. Which means that the person wearing the mask is NOT ill.
3) The person wearing the face masks is suffering from hay fever caused by pollen. Hay fever does not spread to others.
Before Corona virus, Japanese who did not suffer hay fever did not wear face mask at all and may be you can see just 10% of the passengers wearing on metro during winter - flu season.
Face masks were sold all seasons at any drugstores and it was very affordable price to buy before the crisis. However, when the outbreak came to Japan, people rush to stores and bought the face masks as much as possible therefore many stores ran out of the face masks.
Anyway, it is hard to get in Europe and I recommend you to buy it in Japan during your stay to prepare the next virus to come. Preparation and prevention are always welcomed.