There are countless stories of the emotionally weak heroine falling in love with some popular playboy, so it just comes down to who can pull it off better. I think Miyasaka did a good job.
There were undeniable cute parts and their relationship seems very grounded. They fought a lot, I would have been more annoyed if they didn't. Both of them had family problems, which gave it just enough drama. Kiriya seemed to have liked Karin BEFORE she took her glasses off, thank god because I hate superficial characters. This made a good bases for the story.
The story moves at a decent pace, though I think they might have fallen in love too fast. The only thing I did not like about this story was Karin's sudden personality change. At the beginning of the story she was quiet, but cynical. She did not fall for Kiriya's charm and she did not care how she looked. She may have been weak to Yuka, but she was strong in her own way. If only because she saw through people's utter bullshit.
But this changes. Remove her glasses and she becomes a beautiful bimbo. She suddenly gets a fashion sense and she becomes clingy and whiny. She becomes utterly lost without Kiriya guiding her and motivating her. I found it annoying, but I guess her "kind personality"(which I'm not sure when that developed), made up for it.
It's like people wanted to hate her but couldn't, so they ended up helping her instead. Which is just ridiculous. I don't mind the fact that she became beautiful, but I would have liked it better if she weren't so...weak. She has no problem standing up to Kiriya, she even grows a pair and stands up to her parents a few times, but it seems like she's just weak to everyone else.
All in all, I give it a 8/10. I still enjoyed it, dispite this. Karin wasn't completely hopeless and I leveled with her in some aspects. Give it a shot.