https://www.fmscout.com/a-japan-league-system-fm24.html
Before starting the game, you must delete the following files.
C:\Program Files (x86)\Steam\steamapps\common\Football Manager 2024\data\database\db\2400\dbc\permanent
j league non player.dbc
japan.dbc
japan_loans.dbc
1_japan_removed_clubs.dbc
japan_fake.dbc
For instructions on how to delete files, refer to the following webpage.
https://www.fmscout.com/a-fm24-real-names-license-fix.html?e=page#c86019