Nobuhiro had been getting up himself, watching Hayato's struggle from above. The kid was in a bad condition. The more he was trying to not let it show, the more obvious it was to Nobuhiro. Silly.

In the second he had to react when Hayato stumbled, Nobuhiro contemplated just letting the kid fall down to the ground again, but then he decided against it. Instead he took a step over and steadied Hayato a bit, just a bit, with an unreadable expression.
It wasn't anything he did out of compassion or liking, but more of a sign showing how superior he was in every way. It was silly to have these silent battles with a child and that was why he would make no comment, the knowledge was just for himself.