As someone that didn't see the anime or the manga, I didn't have any big expectations but was still quite disappointed.
The story could have been so much better but there wasn't really any development. The characters didn't really bond in any way and each time a new character was introduced, it's so brief you don't even have time to learn about them and think about if you like them... Also, you never learn anything about them, you just get to know what role they play (friend, sister, etc. not much more)
The acting wasn't so good, i cringed so bad even tho i'm a sucker for corny romances. I'm not sure how the main guy is in the anime, but here, he is so hateable : never acts or says anything nice and always talking to the girl like she's a dog... Till the end.
Another complaint of mine is the way it was filmed. For some reason, there was an overuse of extra long shots. A lot of interactions were filmed using extra long shots, resulting in me being confused on what i was looking at and even who i was looking at.
I found myself speeding through the second half of the movie since it got boring and had too many filler scenes.