This shows the schedule for rugby games in Kumamoto. As you can see, games will be played here on the 6th and 13th of October.
I found a link that took me to this schedule in a New York Times article entitled
Rugby World Cup Shines Spotlight on a Less-Traveled Japan Matches will be played in host cities across the country, but Kamaishi, Kumamoto and Fukuroi offer charming destinations and special deals. https://www.nytimes.com/2019/08/14/travel/japan-rugby-kamaishi-kumamoto-and-fukuroi.html
For people already in Kumamoto, the introduction to the area probably doesn’t contain much that you don’t already know.
– Kirk