The Japanese government reaction to the growing threat to public health posed by the Covid-19 pandemic has puzzled foreign observers. Indeed, even after the nationwide declaration of emergency, the measures that can be adopted by both the central and local government have no binding force. In other words, they can only request people to self-isolate at home, without any sanction in case of violation. Hence, the Japanese experience can be defined as a soft lockdown, in comparison with both the Western and the Chinese hard one. The article, after having provided a constitutional and legislative framework, analyses the impact of the emergency declaration on the branches of government and on the private sphere and discusses the Japanese lockdown as an ethical rather than a legal lockdown.