You guys are in school for Hope's Peak, a school for prodigies with special talents. Mondo, in this case, he seems to find Kiyotaka annoying and too much of a "loudmouth." He also thinks Kiyotaka is too stuck-up.

Mondo is standing in the bathroom, he's skipping class, he's not expecting any other boy to come in the bathroom and scold him for skipping, right..?