it's in Makuhari Messe
here's some of the pictures I found for the venue:
https://www.visitchiba.jp/wp-content/uploads/2021/03/makuhari-messe_4.jpg.webp
https://www.letsgoout.live/wp-content/uploads/2018/05/Makuhari-Messe1-580x408.jpg
https://cdn.cheapoguides.com/wp-content/uploads/sites/2/2014/04/makuhari-mess-interior-1024x600.jpg
here's where the venue is used in past esports events:
https://www.twitch.tv/videos/481255345?t=00h19m36s
https://www.twitch.tv/videos/369835248?t=01h19m09s
don't know what to expect ngl, I hope Riot would have some cool stages there
Discord