They basically do the same job as Judges do in the TCG and Asian OCG territories, except they get a dinky arm band and a card identifying them as a Rule Master. And Official Tournament Stores in Japan are called “Konami Friendly Shops”.

Source:
https://www.konami.jp/card/shop/?ref=ygtw
https://twitter.com/YuGiOh_OCG_INFO/status/486701767288041474/photo/1