[FREE SPOILER REVIEW] Uchiage Hanabi is a manga adaptation of the film with the same name, that's based in the 1993's drama. The story of this manga is the same o the anime, with minors differences, but in my opinion, the final of the manga is better explained than the anime. But yes, there's an open-ending, if you dislike anime/manga that has an open-ending, don't read this manga nor anime, you'll dislike it! And in my anime review I write that the story was a little bit confusing, but in the manga isn't confusing, I understand it very better, it's a good thing. The art of this manga ispretty cool; it's very similar to the anime.
To finalize it, I'll tell you something, if you disliked the anime film, you'd (probably) not like manga because as I said, it's very similar to anime.