@RadioForrest
Most of the annoying characters fall into the backdrop, the more the main couple develop their relationship.
For me, the best of the bunch is the principle. He was such a poorly added "villain", a character that's entire purpose was to make sure the main-couple would never become a couple. God forbid, a romance manga would have romance.
It's a good thing the author got his wits about him, and buggered off all of these annoying characters the moment the main-couple actually went somewhere. The principle wasn't needed to stall development and cause needless, redundant conflict -- and what's-her-face-girl didn't really need to push them to be together as bluntly.
They are all still there, but they are not as much of a factor in the story as in the start. I don't recall when she goes from an active match-maker, to a mere spectator, though.