Maybe try here https://tvjapan.net/en/
Also you can check http://www.livesoccertv.com/ they will show on which channels they will show the matches in each country, so when you see the channels for Japan, you can maybe go straight to that channel's website and right now almost all channels have online TV.
Good luck.
All 64 games of Russia World Cup will be shown soon. I need to watch the live broadcasting in Japanese. But now I live in Germany and can not find any Japan TV live service. Online or on iPad both are OK. I also do not mind needing pay for it. A little bit expensive would be OK. World Cup is once every 4 year. It's worth it. What Japan TV service do you guys choose?