I actually liked this and enjoyed it for what it's worth. It's never going to win critical acclaim and people who're after something unique and unpredictable will be greatly disappointed, but this isn't so bad for what it is - a light classic shoujo manga.
There's no strong overarching plot; it basically follows Arisu after she discovers that she's half demon and half angel, and begins searching for her fated partner to stop her problematic physical transformations. Unfortunately, events and settings can feel quite disjointed, particularly in the early volumes - the first dealt with her meeting with a certain boy and was mainly at school, the second introduced rivals that disappeared in the third and was replaced by another new character and a change of scene to a filming set. I think it would've been better if the story had focused more on Arisu's transformation and trying to keep it under wraps - it seems that part was more or less shoved aside later. On the upside, precisely because the plot isn't a strong one, it didn't greatly impact my reading enjoyment. Shrug and move on.
As the previous commenter said, the characters and their relationships could've used more depth. Arisu was okay, but I never got a really good feel for Aoyama outside of his character traits (he's prickly, easily embarrassed, etc.). Arisu's cousins, Asuka and Tsubasa, were chucked aside conveniently after their part as romantic rivals was done, and you almost never saw them anymore. I did like Arisu's little sister Mirai, though - she's hilarious and I wish her chapter at the end of the final volume was translated.
I don't usually talk about endings, but I feel the need to clarify for fans of happy endings that the first comment was completely off. It was definitely a happy ending, and it was frankly fairly clear from the beginning who Arisu would end up with (there was only one guy introduced in the whole first volume!) Perhaps some people might alterna-ship, but I'm pretty sure 9 out of 10 readers would be happy with the final couple. Their relationship developed quite quickly from bickering "enemies" to a friendlier one so it lost the chance to hook me with a steady build-up, but... it was still cute. The whole point was that people were tied together to their fated partners by the "red string of fate", but if your love for someone is strong enough, it's possible to change it.
Basically, don't drop everything you're doing to read this, but if you have a spare moment and you're in the mood, there are far worse options.