The surge in cases (not deaths) in Aug, 2021 coincided with the Olympics in Japan that led to lower compliance of the population in observing protective measures. Groups were gathering in small bars and eateries during the Olympics. It also coincided with the rise of the Delta variant at the same time. Despite this, the death rate stayed very low. Citing only the case rate is misleading. The drop in cases coincided with the end of the Olympics an increased distribution of vaccines and greater compliance with observing protective measures, including such social expectations as people not talking when using mass transportation.
Japan has done lots of things well during the pandemic from which we can learn. They were very quick to use extensive contact tracing and containment measures very early, including quarantines, travel restrictions, distributing masks, and closing schools well before the U.S. Their population was using masks continuously at levels never achieved anywhere in the U.S., They still do. They have low BMIs and don't live on junk food.