Orenji Tachibana's Links
To be blunt; Kiyoshi doesn't really like his attitude. He also really does not enjoy being around him for very long because he absolutely hates lemons and Orenji is constantly smelling like one. Kiyo doesn't exactly appreciate how much he teases everyone in the class (including Kiyoshi himself), and he just wishes Orenji would learn to be kinder and more respectful to other around him. In general Kiyoshi just tries to stay away from him.
Long story short, he absolutely despises him. He finds Orenji to be nothing more than a crass, immature brat who has absolutely no right in deserving of being at a school like UA. Katashi hates his attitude and cant stand his way of speaking to others. He definitely has done little things to piss Orenji off on purpose just to get under his skin, he will admit that. Katashi just wishes he would go away and he's a shining example of how some people just shouldn't be let into hero school, plain and simple.