Many marathon races have been cancelled or postponed since the start of the pandemic, and the Tokyo races are included. Usually the Tokyo Marathon is held in late February or the beginning of March. The Shizuoka Marathon is held either two weeks before or two weeks after Tokyo.
Because so many runners want to participate in the Tokyo Marathon, a lottery is held to choose the participants for the race. A few of my students have run it and the medals are very nice.
In 2020, the Tokyo race was scheduled for March 1st, but due to the corona virus, the race was limited to elite runners only. The race that was to be held in February of 2021, was postponed to October 17th, due to the ongoing pandemic. Because of the State of Emergency in Tokyo, it was just announced that the October race is being moved to March 6, 2022 and will still be called the 2021 Tokyo Marathon. The 2022 marathon is cancelled. Yes, even though the marathon will be in 2022, it will be the 2021 marathon. (Sounds like the Tokyo Olympics).
The registered runners from last year were given the option to participate in this year's race, with an additional fee for PCR testing. I suppose that participants will be moved ahead again, if they choose to participate. I'm sure it is a big disappointment for the confirmed marathon runners. With only a month before the scheduled October 17th race, they are probably in great marathon shape and will need to train anew if they want to participate in the March race. I know there are many marathon runners who keep in great shape all the time, but I also know there are many people who want to run a marathon and are training for the specific race. I guess it can't be helped.