So I read this manga way back in middle school. Don't remember much of the story but I remember it being way more interesting than this movie.
The camera work was bad, it really made no sense. There was no logical transitions to it.
The actors are only get what they're given but it was really dry.
It was shortened from the manga into a 2 hour movie and skips a lot of necessary character development.
Overall it was bad at the beginning, good in the middle, and worse at the end.

go read the manga. not saying it portrays good people and it definitely encourages early 'relations' but it had a decent story. the movie explains nothing in their childhood that leads to the story that is presented to you. And because I read this manga in middle school I definitely looked at this from a semi-adult perspective now that I'm 25 lol