second for mahjong in one hour
world: https://vrchat.com/home/launch?worldId=wrld_c69bade4-f2de-4da1-892a-b499b8798190

LINK graciously borrowed from /mjg/: https://repo.riichi.moe/
and if you don't like reading, here's a starter: https://www.youtube.com/watch?v=mcmQqPhKvWg&t=5s
and his basics playlists: https://www.youtube.com/playlist?list=PLPBLBlC-7G3s92GyGOprSmZ1mqgh0U0DI
(don't worry about the setup)