ESL in Japan and sport

Hello there, I am thinking of working in Japan as an English teacher, but I am also looking to gain more experience in sport coaching or gym assistant, generally any position to do with sport. How easy is it as a foreigner to join clubs or participate as coaches at clubs or school sports, paid or unpaid?

I think you want to work in this kind of business.
https://globalathlete.jp/english-soccer/

Children can learn English and soccer at the same time.

So, you can look for your employer or set up your own business in Japan.