緊急事態下、オリンピックの開催/中止を決定するのは主に主催国側の責任なのでしょうか？　大会の主催者/統括者であるIOCが、主催国のみならず、全参加国の状況を考えて、それぞれの意見をとりまとめ、さまざまな分野の専門家と協議し決定する責任があるのではないかと思います。

Is it mainly host country’s responsibility to decide whether to hold/cancel/postpone the Olympics under the current state of emergency? I think it is the IOC, the principal organizer’s responsibility, to make such an important decision based on the opinions of not only the host country but also of each participating member country as well as medical and other professional advisors around the world in connection with the pandemic. The Olympics is not a Japanese event. It’s an international event.