It is scheduled to be held at the citizen's plaza beside the tokyo metropolitan assembly building.IOC vice president, John Coates and IPC vice president, Andrew Parsons will attend.
Perhaps After the ceremony, it will be released on youtube.
Sep - Oct, 2015 : Formulation of the new construction plan and the international design competition open
Jan - Feb, 2016 : Design unveiled
Spr - May, 2020 : Completion
May- Jun, 2020 : Test event
very tight schedule.