Does the Japanese competition crash in game, or are you getting any errors in the editor when verifying the DR Congo rules?
The validation tab gives information, but does not mean your file is corrupt, wrong or anything. However, if you also try to play the Japanese competition in game, when there are changes in this file with regard to the Japanese competition, it might crash.
This is what the default (20.4) database shows when I open a random Japanese University team. The Secondary Division is filled. The Division is not filled.
If any of your changes in your database is that both the Division and Secondary Division are filled for Japanse university rules, that's what's causing the issue with the Validiation list and likely will cause the issue with Japan crashing, as the competition rules will not work properly.