Complex sentence: The term has been also frequently appeared in sports in Japan since late 20th Century, including sumo where there has been no Japanese-born yokozuna since 1998 and no Japanese-born champion since 2006 as most of the top players have been from Mongolia or Polynesia.
Split into simpler sentences: The term has been also frequently appeared in sports in Japan since late 20th. Including sumo where there has been no Japanese-born yokozuna since 1998 and no Japanese-born champion since 2006 as most of the top players have been from Mongolia or Polynesia.