With shadow clones Naruto feels like it would be a PRIME choice to reference it.The 100 Man Kumite is actually a really cool challenge, and I'm glad to see it used, or at least referenced, here. I'm actually shocked more shonen manga don't use it or bring it up. You could have easily seen a scene like this in Bleach or Naruto, but you never did. Hell, I don't even think I've seen it used in most actual martial arts manga, like Baki.