Fuji room might work https://www.meijikinenkan.gr.jp/english/partymice/venues/
Discussion
Tokyo Big Sight is another option to look into. I’d be shocked if it was completely booked during that window. https://www.bigsight.jp/english/organizer/facilities/
(Threads appear different on here than Twitter so I hope you’re seeing these lol) There’s also Tokyo Prince Hotel. Ho-O-No-Ma (Main Hall) specifically https://www.princehotels.com/tokyo/meeting/ho-o-no-ma-main-hall/
Belle Salle Shiodome has a lot of options (select 500-1000 attendee count in the dropdown)
