So imagine this:
Some other team is making fun of Hinata's height, and he's just like, "We're gonna crush you" etc.
Then Kage realizing that they were making fun of Hinata, and coming up behind him mouthing, "Back the fuck up away from my boyfriend if you know what's good for you."
And then Hinata not realizing that Kage was behind him and thinking that he scared the other team off by himself.