You have an overly rosy picture of Japan. Their population is very compliant and already used to masks as a way to avoid spreading disease, and they are still e

You have an overly rosy picture of Japan. Their population is very compliant and already used to masks as a way to avoid spreading disease, and they are still experiencing a surge in cases that has caused them to declare a state of emergency in the Tokyo area, and remove spectators from the paralympics. Herd immunity happens when a disease can't spread because all people surrounding the infected person have enough immediate immunity to stifle its progress. Delta seems to be able to spread to people in the gap before the immune system recognises it, so it may be something that can't be stopped by herd immunity.