Watched it after reading the manga. From what I remember there were no changes which is great.
The thing is that the part of the manga that this movie explores, has a terrible event. The fact that they sound director didn't chose a dark music during that event but a completely opposite one made me disgusted. (*specifications on what that event was at the end of the review)
The animation is the same as in the series except for a higher quality during the performance. Voice acting was good. Sound design was normal. Soundtrack good (great performance song, awful choice during prior mentioned event).
Charcaters: The relationship between the three main characters were complex and realistic enough. Ugetsu's reasoning and actions are understandable and painful; Akihiko's event was disgusting while his character development was good to see but should have been explored more; Haruki is a good person.
Overall decent and faithful adatation but, again, the music decided on during the event made me dislike the entire movie.
*SPOILERS (mention of said event):
Akihiko sexually abusing and almost raping Haruki was awful to see while reading the manga. Akihiko didn't apologize nearly enough and then had the face to ask to stay in Haru's place. But that's a complaint I have with the original source so I can't really talk about that whenreviewing the movie. What I can complain about is the use of a happy/sexy song while the abuse was happening. Truly disgusting.