It was cute - but it only gets a 6/10 from me. (If I could use decimals, it'd be closer to 6.5 or so, though)
Here's my opinion (spoiler-free!)
The story is decent, the art is fairly shoujo, and it is cute. However, the main thing about the manga is the main character. I don't dislike her - I actually find her cute! The only issue is that her problem with badmouthing people is to the extent that it seems like someone put a curse on her. She has the words in her head she wants to say, but what comes out is a twisted mean version of it. In fact, it's so bad that most of her words throughout the manga are thinking or narration - and aside from that she makes an effort not to speak unless spoken to if she can help it.
I feel like this fact alone takes over the whole manga in a way. While I want to focus on the love story between the main characters, or the cute antics of side characters - I can't do so without also noting that almost everything that happens is due to her bad mouth.
It's to the point that the summary would be almost more accurate if it was something more like, "This is a love story about a girl who had a spell cast on her, making her only able to say nasty things - and she must get through school life with this terrible curse!"
(Well - except magic doesn't exist in this manga. She's supposed to just have this problem from hanging out with a lot of brothers growing up or something.)
ON THE OTHER HAND...
Don't get me wrong. It IS a cute read. Positives are that if you view this as a purely fun/cute love story about something silly like "a girl who can only insult people", then you could have a good time. Her love interest is an adorable character and deals with her well, and there's something intriguingly happy about how he's able to stand her. Because her bad mouth feels entirely involuntary to the point that she seems like a victim of her own habits, his kindness is always appreciated and it helps you cheer them on.
I might actually buy this manga to have it on my shelf if I'm ever bored and want to read, but it isn't on my top-favorites at the moment.
Still, it's all up to you if you want to check it out. I do recommend it, just for the cute read.
