I think this comes at good timing because I just finished route: Masato only a few hours after reading this. And it comes at a big surprise because, all this time, I thought it was Kengo who couldn’t stand Haruka! Whereas Masato was just putting up with her shit. Guess it was the other way around, huh. It is Masato who forcefully kicks her out of his room, after all.
And I think this goes in to his story and how he forces himself to be stronger to escape the scorn of idiocy. After all, he is very much an idiot; i don’t think he denies that, and he is reminded of it every time Rin gives him a dropkick for being an idiot. But I think, more than Rin, the only thing that can shove his own idiocy in his face are pranks, which are exactly Haruka’s specialty. I don’t blame Haruka for that; her simple pranks would make anyone feel like an idiot, and most people would just laugh it off or get ticked off for a few minutes. But it brings back Masato’s in-grained insecurity for him in a way that I don’t think he finds acceptable.
And maybe that’s why he can’t stand Haruka. And it’s funny how we learned this from a route with a totally different writer from Masato’s own route.
Man, Little Busters’ writing sure is tight 
