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
Source:
https://www.konami.jp/card/shop/?ref=ygtw