Takanori Nagase and Soichi Hashimoto each earned a gold medal on the second day of action at the Montreal Judo Grand Prix on Saturday.
In the men's 81-kg class, Nagase, who won bronze at the Rio Olympics, scored five consecutive ippon wins at the Montreal Olympic Park, including in the quarterfinal when he beat Germany's 2017 world champion Alexander Wieczerzak.
In the men's 73-kg event, 2017 world champion Hashimoto won all his four bouts by ippon, capping the feat by defeating 2014 world bronze medalist Victor Scvortov of the United Arab Emirates in the final.
In the women's 70 kg event, Japan's Nanami Asahi finished seventh.
Hashimoto and Nagase's victories are the third and fourth titles for Japan at the event after Naohisa Takato and Wakana Koga won the men's 60 kg and women's 48 kg divisions, respectively.
The four golds put Japan on top of the medal table ahead of five nations with one win each.
A total of 249 judoka from 50 countries are competing in the July 5-7 event.