There are school and university competitions. I was on the squad of the Gakko Kyoshi Kendo Renmei. (School Kendo teachers association) Police have competitions and also gekiken type anything goes matches.
Nationals are usually dominated by a prefectural representative who has already graduated university and is probably in the Police or education. They are usually 5th \6th Dan. Ranks have been revised now by the association with the highest being 8th Dan. Before it was up to 10th. There is a yearly not to be missed 8th Dan competition, with the best in country competing.
Retirement from active organizing is 65 to have younger people step up to do the job. We can split Kendo into age brackets to determine what one is trying to achieve. 20/30 30/40 and so on. With age we are looking for perfection and quality in what we do rather than quantity.
I have to say I was a late starter. I never though I would catch up. Already Dan graded in my 20s but getting the crap beat out of me by police riot squad guys. But ten practices a week brought me up to par and above. Most of all my age had already taught me to use my brain to fight and not expend useless energy.
Below in one of my old high school kendoka Nishimura Ryutaro at the nationals. But the credit goes to both his mother and father who were national champions.