Hmm... All the heroines have a little tsundere in them. Even the protagonist might have some too at one point. I actually like the characters... even Ryou after playing her route... but she's still my least favorite.
As for the story, I feel a lot of the time it kept me thinking something big might happen, but instead it just didn't. So the story is kind of lacking, but I still enjoyed it. I also started liking the protagonist more after seeing some of his backstory.