There are 15 Judo gold medals up for grabs at the 2024 Summer Olympics. There are 7 weight divisions in each of the Men's and Women's competitions, and a Mixed Team event. If Japan wins at least 8 of these 15 medals, then this market will resolve to YES.
Looking at the results for previous years (https://olympics.com/en/olympic-games):
2008 - 4/14 wins
2012 - 1/14 wins
2016 - 3/14 wins
2020 - 9/15 wins
As for total gold medals (https://en.wikipedia.org/wiki/Judo_at_the_Summer_Olympics#Competition_format):
Japan - 48
France - 16
South Korea - 11
Japan definitely is the dominating country in this category, and the Tokyo 2020 showing was spectacular (potentially because of excitement from home field advantage), though >50% gold again seems unlikely due to the wide spread of other countries vying for gold, especially looking at performance for the years 2016 and below